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Opening remarks

New Frontiers in Big Bang Nucleosynthesis - Catching Up with Cosmology and Astronomy

• Steffen Turkat (Technische Universit¨at Dresden, Germany)

Big Bang Nucleosynthesis (BBN) describes the formation of the light elements during the first minutes of the Universe and provides one of the earliest tests of the standard cosmological model. Together with observations of primordial element abundances, nuclear reaction data and theoretical calculations, BBN provides a unique framework for testing the concordance between cosmology, astronomy, and nuclear astrophysics. In particular, the primordial deuterium abundance enables an independent determination of the cosmic baryon density and constitutes one of the most stringent tests of modern cosmology. Following recent advances in the determination of the 2H(p, γ)3He reaction rate, the 2H(d, p)3H and 2H(d, n)3He reactions now dominate the nuclear uncertainties in BBN calculations. While astronomical observations of primordial deuterium have reached percent-level precision, the nuclear reaction data still has not kept pace. Nuclear physics has thus become the limiting factor in exploiting BBN as a precision probe of cosmology. To address this challenge, the DT neutron generator at Technische Universit¨at Dresden is currently being upgraded from a dedicated 14 MeV neutron source into a multi-purpose accelerator facility for fusion research, neutron activations, and nuclear astrophysics. Its deuteron beam, covering energies from 10 keV to 350 keV, will enable measurements of both deuterium fusion reactions over the entire energy range relevant for BBN. This talk will present an overview of the role of BBN as a multidisciplinary probe of modern cosmology and highlight the new experimental program at the DT neutron generator of TU Dresden.

New measurements for Big Bang and stellar nucleosynthesis at Felsenkeller

• Eliana Masha

The primordial abundances of light elements produced during Big Bang Nucleosynthesis (BBN) provide a powerful probe of the cosmological baryon density. Precise nuclear reaction data for these processes are essential to constrain the models. Among these, the 2H(p, $\gamma$)3He and D+D fusion reactions govern the deuterium abundance and are the key sources of uncertainty in its predicted primordial value, while the 3He($\alpha$, $\gamma$)7Be reaction determines the primordial 7Li abundance. The latter reaction is also a key process in solar hydrogen burning, directly influencing the predicted solar neutrino fluxes. The 2H(p, $\gamma$)3He reaction has been the main source of uncertainty in deuterium destruction for many years. It was previously measured at BBN energies by the LUNA collaboration using a windowless gas-target system, covering energies of 33–270 keV. However, higher-energy measurements with solid targets show a 10% disagreement, revealing a tension between the low- and high-energy datasets. To resolve this discrepancy and to provide new data for theoretical ab-initio calculations, a new measurement was performed at the Felsenkeller underground laboratory in Dresden, Germany, covering energies of 200–1200 keV and partially overlapping the existing datasets.Using a similar setup, the angular distribution of the 3He($\alpha$, $\gamma$)7Be reaction was also studied at energies of 442–1213 keV. This talk will present an overview of BBN and the related nuclear measurements at the Felsenkeller underground laboratory in Dresden. Goals, experimental setups, new results from 2H(p, $\gamma$)3He and 3He($\alpha$, $\gamma$)7Be measured at Felsenkeller as well as future plans will be shown.

The Li-7 photodisintegration and New Photonuclear Studies at HIγS (YRP)

• Ioana Kuncser (ELI-NP (IFIN-HH) / UNSTPB)

The abundances of the light elements are predicted by the Big Bang Nucleosynthesis (BBN) and can be spectroscopically determined by observing the low-metallicity stars. Usually, the measurements are in agreement with the BBN predictions. Particularly, the Li-7 measured abundance is 3-4 times lower than expected, discrepancy known as the “cosmological Li problem”. The reaction $^3$H(α,γ)$^7$Li contributes to the production of Li-7 in Universe and can be studied through its inverse reaction, according to the reciprocity theorem. The Li-7 photodisintegration has been measured by our team once in 2017 and then again in 2023 at the High Intensity γ-ray Source (HIγS) Laboratory of Duke University (USA), using a silicon detector array (SIDAR) to observe coincidences between alpha particles and tritons. In 2023, the reaction was measured for gamma-beam energies between 3.7 and 6 MeV. The set-up and the results of the experimental campaign carried out at HIγS in 2023 will be presented. In addition, a new experiment conducted in 2026, enploying a similar set-up will be discussed. The latter focuses on the measurement of photonuclear reactions (γ,p) and (γ,α) on different targets as Sn-116 and Sn-120.

New insights on indirect studies of the 𝛼(d, 𝛾)6Li radiative capture (YRP)

• Monica Sanjinez Ortiz (JGU Mainz)

The radiative capture reaction 𝛼(d, 𝛾)6Li plays an important role in the early-Universe production of lithium and other light nuclei and has therefore been subject to extensive experimental and theoretical investigations. Its cross section was measured directly in the range of astrophysical relevance for the first time in 2014 by the LUNA collaboration [1]. Earlier two attempts to determine the cross section indirectly via Coulomb dissociation were performed as this process can be understood as the time reversed process of radiative captures [2,3]. With a fully dynamical reaction model, we report here on a new theoretical analysis of these Coulomb dissociation experiments. Our results indicate that the breakup of 6Li onto 208Pb at 150 A MeV and 26 A MeV is characterized by marked Coulomb-nuclear interferences. Moreover, the analysis points towards a nuclear dominated process at forward angles as Coulomb breakup is suppressed due to the 𝛼-d clustered structure of 6Li. Furthermore, we confirm the relevance of higher-order effects in the breakup process. Consequently, extracting radiative capture cross sections from data at these energies is unfeasible. The forward Coulomb breakup suppression may be a general feature of breakup processes involving N=Z clustered nuclei. We underscore the importance of alternative indirect methods for the determination of cross sections for astrophysics such as photodissociation induced by electrons. [1] M. Anders et al. (LUNA Collaboration), Phys. Rev. Lett., 113, 042501 (2014). [2] J. Kiener et al., Phys. Rev. C, 44, 2195 (1991). [3] F. Hammache et al., Phys. Rev. C, 82, 065803 (2010).

Recent measurements of reaction cross-sections at astrophysical energies using the ELISSA array

• Haridas Pai (Extreme Light Infrastructure - Nuclear Physics (ELI-NP), IFIN-HH)

ELISSA is a 4π silicon strip detector array implemented at the ELI-NP facility for measurements of photodissociation reactions using high-brilliance, quasi-monoenergetic gamma beams [1, 2]. Direct measurements of the 7Li(p, α)4He [3] and 6Li(p, α)3He reactions related to the "Cosmological Li problem" as well as 11B(p, α)αα and 19F(p, α)16O reactions at astrophysical energies were performed at the Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH) using a scaled-down version of the ELISSA detector array and the 3 MV Tandem accelerator. The thermonuclear reaction rates of 7Li(p, α)4He and their uncertainties were computed. It has been shown that the present DWBA prediction results in 5%–25% difference in reaction rate below T9 = 0.2. In this talk, recent measurements of reaction cross-sections at astrophysical energies using the ELISSA array will be presented. References: [1] S. Chesnevskaya et al., Journal of Instrumentation 90 T05006 (2018). [2] T. Petruse et al., Nucl. Instrum. Methods Phys. Res. Sect. A 1086, 171317 (2026). [3] H. Pai et al., Phys. Rev. C 113, 045804 (2026). Acknowledgment: This work was supported by the Romanian Ministry of Research and Innovation under research contract PN 23 21 01 06 and by the Romanian Ministry of Research, Innovation, and Digitalization, Project no. PN-IV-P2-2.1-TE-2023-0144, within PNCDI IV.

Photonuclear reactions for ultra-high energy cosmic-ray propagation and disintegration

• Par Anders Soderstrom (ELI-NP)

Meteoritic isotopic anomalies as precision tests of stellar nucleosynthesis

• Nan Liu (Boston University)

Meteoritic isotopic anomalies preserve the isotopic fingerprints of stellar nucleosynthesis before and during Solar System formation. In presolar grains, these signatures can be measured in individual stellar condensates, while bulk meteorite components and leachates record the incomplete mixing of distinct nucleosynthetic carriers in the solar protoplanetary disk. Together, these materials provide some of the most precise laboratory constraints on neutron-capture nucleosynthesis, stellar evolution, and Galactic chemical evolution. In this invited talk, I will give a broad introduction to meteoritic isotopic anomalies and discuss recent collaborative efforts to revisit several long-standing discrepancies between meteoritic data and asymptotic giant branch star (AGB) predictions. Using updated neutron-capture information from the n_TOF and Back-n facilities together with FRUITY AGB models, we found that several previously unresolved isotope systems can now be brought into good agreement with meteoritic constraints. These include Dy isotopic anomalies in meteorite leachates, Mo–Nb systematics relevant to 94Mo/92Mo in presolar SiC grains, and the 64Ni enrichments of AGB-derived SiC grains. Although these cases all point toward improved agreement between meteoritic data and AGB nucleosynthesis, the underlying causes of the earlier discrepancies are different. For Dy isotopes, the mismatch was likely amplified by limitations in early meteoritic measurements, including unresolved isobaric interferences. For Ni isotopes in presolar SiC grains, earlier measurements were affected by solar Ni contamination, whereas new Ni isotope data reveal intrinsic AGB signatures consistent with FRUITY predictions when updated 64Ni neutron-capture constraints are used. For the Mo–Nb system, the key issue lies instead in the inaccurate treatment of the temperature-dependent β− decay rate of 94Nb in previous AGB models, which limited the production of 94Mo through the β− decay channel. I will also discuss how the new Ni isotope measurements of presolar SiC grains extend beyond AGB nucleosynthesis. In particular, correlated 60Ni enrichments in selected grains provide isotopic evidence for local Type Ia supernova pollution of the parent molecular clouds from which their parent stars formed. These results show how meteoritic isotopic anomalies can be used not only to refine nuclear inputs and stellar models, but also to trace the evolving contributions of different stellar sources to Galactic chemical evolution.

Cosmic gamma ray spectroscopy lessons on stars and supernova ejecta

• Roland Diehl (MPE Garching and TU Munich)

Nucleosynthesis from cosmic sources is encoded in the variety of isotopes, some of which we can observe today. Space-based gamma-ray telescopes have observed nuclear emission from freshly-produced and unstable isotopes as they decay in interstellar space. Short-lived 56Ni and 44Ti has been measured in supernovae, and help understand the complexity of launching a supernova, for the thermonuclear and for the core-collapse type. More long-lived 26Al and 60Fe accumulates from many such sources, and tells us about the cumulative output from massive-star clusters, and about pre-supernova burning stages within the massive stars. In this talk we will discuss what has been learned from more than two decades of nuclear gamma ray spectroscopy on the interiors of stars and supernova explosions, and on how they spread new nuclei in interstellar space. We will also address how this astronomical technology works, and how it can be advanced.

From Asteroids to Earth: Reading the Diary of a Meteorite

• Silke Merchel

The presence of long-lived radionuclides in meteorites is the result of their interaction with cosmic rays. Consequently, the concentrations of these cosmogenic nuclides (CNs) reflect the extraterrestrial matter's irradiation history. The reconstruction parameters of interest are: 1. pre-atmospheric size and shielding depth of the body in space (meteoroid) 2. irradiation time in space (irradiation age) 3. identification of complex exposure, i.e., repeated collisions or inherited CNs from pre-exposure at the surface of the meteoroid’s parent body (asteroid, Moon, Mars) 4. residence time on Earth (terrestrial age) for meteorite finds. Accelerator Mass Spectrometry (AMS) is the method-of-choice for detecting long-lived CNs such as ¹⁰Be, ¹⁴C, ²⁶Al, ³⁶Cl and ⁴¹Ca with half-lives ranging from 6 ka to 1.4 Ma. However, tedious radiochemical separation [[1]] to deplete matrices and isobars was previously a prerequisite for AMS preventing fast and reasonable analysis. Now, the world-wide unique Ion-Laser InterAction Mass Spectrometry (ILIAMS) system, developed at the Vienna Environmental Research Accelerator (VERA), provides isobar suppression by up to fourteen orders of magnitude [[2]]. Hence, ILIAMS-assisted AMS, enables the direct detection of ²⁶Al/²⁷Al (~10^-10) and ⁴¹Ca/⁴⁰Ca (~10^-11) in crushed stony meteorites containing ~1% intrinsic Al and Ca. Because ILIAMS suppresses the naturally abundant isobars (~15% Mg, ~1‰ K) so effectively, tedious radiochemical separation is no longer necessary. This approach has been successfully applied to recent European meteorite falls like Drélow, Elmshorn [[3]], Haag [[4]], Kindberg, Koblenz, Ribbeck [[5]] and Saint-Pierre-le-Viger [[6]], as well as to meteorite finds. We can also quite easily decipher true meteorites from meteor-wrongs [[7]]. Most remarkably, a stacked-foil detector allowed the use of Be²⁺ (rather than Be³⁺), thereby, boosting ¹⁰Be measurement efficiency by an order of magnitude. We are proud to announce a promising new *"hydrofluoric acid (HF)-free"* method for ¹⁰Be analysis in stony meteorites, which aims to minimise hazardous chemistry for this widely accepted radionuclide. For iron meteorites, chemistry is still needed, but ILIAMS allows easy isobar suppression and very efficient ³⁶Cl, ⁴¹Ca and ²⁶Al (by high current AlO^-) determination. Other CNs such as ⁵³Mn (t_1/2=3.7 Ma) and ⁵⁹Ni (t_1/2=0.1 Ma) are currently under investigation. The latter will be an ideal nuclide to determine longer terrestrial ages exceeding the typical 50 ka limit of (often troublesome for iron meteorites) ¹⁴C dating. The validation of ⁵⁹Ni dating by alternative methods such as ³⁶Cl-⁴¹Ca-dating [[8]] is work-in-progress on a larger set of iron meteorites including Agoudal, Hoba, Kunova Teplica, Santa Catharina, Smolenice, and – yet unpublished - recent finds. *Acknowledgments:* We thank A. Bischoff, D. Heinlein, L. Ferrière, A.J. Jull, M. Patzek, A. Patzer, P.P. Povinec, and J. Zipfel for very valuable meteorite samples, and the VERA team, especially S. Adler for assistance with AMS. *References:* [\[1\] Merchel & Herpers, *Radiochim. Acta* (1999).][1] [\[2\] Martschini et al., *Radiocarbon* (2022).][2] [\[3\] Bischoff et al., *Meteorit. Planet. Sci.* (2024).][3] [\[4\] Bischoff et al., *Meteorit. Planet. Sci.* (2025).][4] [\[5\] Bischoff et al., *Meteorit. Planet. Sci.* (2024).][5] [\[6\] Egal et al., *Nat. Astron.* (2025).][6] [\[7\] Pittarello et al., *Meteorit. Planet. Sci.* (2025).][7] [\[8\] Smith et al., *Meteorit. Planet. Sci.* (2019).][8] [1]: https://doi.org/10.1524/ract.1999.84.4.215 [2]: https://doi.org/10.1017/RDC.2021.73 [3]: https://doi.org/10.1111/maps.14193 [4]: http://doi.org/10.1111/maps.70060 [5]: https://doi.org/10.1111/maps.14245 [6]: https://doi.org/10.1038/s41550-025-02659-8 [7]: https://doi.org/10.1111/maps.70030 [8]: https://doi.org/10.1111/maps.13417

Exclusive Indirect Measurement at the ISAC-II Facility of the 22Ne(α,γ)26Mg Reaction for s-process Nucleosynthesis

• Thomas Chillery (University of Naples)

Around half the elements heavier than iron originate from the astrophysical slow neutron-capture (s-) process. This mechanism occurs within the stellar environments of asymptotic giant branch and massive stars, where the endothermic 22Ne(α,n)25Mg reaction is one of the main sources of neutrons. This reaction competes with 22Ne(α,γ)26Mg across the astrophysical temperature regime 150 – 300 MK (Ecm = 300 – 750 keV). To constrain both the temperature at which neutron production is activated and how much 22Ne is converted to neutrons, it is essential to understand the contribution of resonances to the reaction rates. Several resonances for these 22Ne+α reactions have been directly measured down to Ecm = 706 keV. However, below 700 keV there remains considerable disagreement between experimental studies on the resonance strengths of crucial states. To confront this weakly-constrained energy region, at the ISAC-II beamline in TRIUMF (Canada) we performed a dedicated study of crucial 26Mg states using the indirect 22Ne(7Li,t)26Mg reaction. A 22Ne beam at 3 MeV/nucleon bombarded a 500 μg/cm2 LiF target, following which the gamma-rays and 26Mg recoils were measured using the TIGRESS and EMMA systems, respectively. The tritons were detected at backward laboratory angles using a Micron S3 silicon detector. We will present the setup and preliminary analysis from this study, the results of which are expected to enhance our understanding of these essential neon-burning reactions in stellar nucleosynthesis.

Neutron capture reactions in the s-process: recent experimental breakthroughs and future projects

• Jorge Lerendegui Marco (Instituto de Física Corpuscular (CSIC-UV))

Neutron-capture cross sections are a key nuclear-physics input for modelling the slow neutron-capture process, which is responsible for the production of about half of the elements heavier than iron in red-giant and massive stars [1]. In particular, unstable branching-point nuclei provide a sensitive probe of the physical conditions in stellar interiors, because neutron capture competes with $\beta$ decay and the resulting isotopic abundance pattern depends on the local temperature and neutron density. The long-lived isotope $^{79}$Se, with a terrestrial half-life of 3.27(8) $\times$ 10$^{5}$ y [2], is one of the most relevant and debated s-process branching points [3]. Located in the transition region between the weak s-process in massive stars and the main s-process in asymptotic giant branch stars, the $^{79}$Se branching controls the flow toward the s-only isotope $^{80}$Kr through $\beta$ decay or toward $^{82}$Kr through neutron capture [4,5]. Owing to the strong thermal dependence of the $^{79}$Se $\beta$-decay rate, an accurate $^{79}$Se(n,$\gamma$) cross section can provide stringent constraints on the stellar temperature by comparison of model predictions with Kr isotopic ratios measured in presolar SiC grains [5,6]. In addition, $^{79}$Se is relevant for nuclear-transmutation studies because of its contribution to the long-term radiotoxicity of spent nuclear fuel [7]. Despite this relevance, no experimental data existed so far for $^{79}$Se(n,$\gamma$), and the available MACS values relied entirely on theoretical estimates [8]. Direct activation is not feasible because the reaction product $^{80}$Se is stable, making time-of-flight the only direct experimental approach. In this context, the first-ever measurement of this cross section was proposed at CERN n\_TOF [9]. Among the experimental challenges, only about 2.7 mg of $^{79}$Se were available in a PbSe alloy sample produced from neutron irradiation of enriched $^{78}$Se at ILL [9]; the $^{79}$Se/$^{78}$Se ratio is very small, with $^{78}$Se representing about 99.7% of the selenium content; the sample activity produces a large background, with an important contribution from $^{60}$Co; and the large amount of $^{208}$Pb in the sample leads to a strong neutron-scattering background relative to the capture signal. These limitations have only recently become tractable thanks to the combination of the high instantaneous neutron flux of the upgraded CERN n\_TOF-EAR2 beam line and advanced detection systems developed for high-sensitivity capture measurements [10-13]. In this contribution, we present the results of the successful n\_TOF measurement, which took place in both time-of-flight beam lines EAR2 (19 m) and EAR1 (185 m). The EAR2 measurement using the new segmented sTED array [13] in a compact ring configuration [14] provided the sensitivity required to overcome the activity background and made it possible to achieve low statistical uncertainties [10]. Moreover, the high-resolution EAR1 measurement with the Compton-imaging i-TED [11,12] array enabled improved control of neutron-induced background and systematic effects related to dead time and energy resolution [10]. The analysis of the capture yield in the resolved-resonance region has led to the observation and analysis of more than ten resonances of the $^{79}$Se(n,$\gamma$) cross section for the first time. The resulting resonance parameters have been used to derive a semi-empirical cross section, thereby providing the first experimental constraints on the Maxwellian-averaged cross section over stellar temperatures relevant to AGB and massive-star nucleosynthesis. The results from this analysis will be presented for the first time in this contribution. **References** [1] F. Käppeler et al., Reviews of Modern Physics **83**, 157 (2011). [2] G. Jörg et al., Applied Radiation and Isotopes **68**, 2339--2351 (2010). [3] F. Käppeler et al., Reports on Progress in Physics **52**, 945 (1989). [4] G. Walter, H. Beer, F. Käppeler et al., Astronomy \& Astrophysics **167**, 186 (1986). [5] R. S. Lewis et al., Nature **348**, 293 (1990). [6] N. Klay and F. Käppeler, Physical Review C **38**, 295--306 (1988). [7] W. S. Yang, Y. Kim, R. N. Hill, T. A. Taiwo, and H. S. Khalil, Nuclear Science and Engineering **146**, 291--318 (2004). [8] Z. Y. Bao, H. Beer, F. Käppeler et al., Atomic Data and Nuclear Data Tables **76**, 70 (2000). [9] J. Lerendegui-Marco et al., CERN-INTC-2020-065 / INTC-P-580 (2020). [10] J. Lerendegui-Marco et al., EPJ Web of Conferences **279**, 13001 (2023). [11] C. Domingo-Pardo, Nuclear Instruments and Methods in Physics Research A **825**, 78--86 (2016). [12] V. Babiano, J. Lerendegui-Marco et al., European Physical Journal A **57**, 197 (2021). [13] V. Alcayne et al., Radiation Physics and Chemistry **217**, 111525 (2024). [14] J. Balibrea-Correa et al., Nuclear Instruments and Methods in Physics Research A **1072**, 170110 (2025).

Neutron induced reaction measurements for nuclear astrophysics

• Claudia Lederer-Woods (School of Physics and Astronomy, The University of Edinburgh)

Neutron induced reactions play a key role in the production of the heavy elements (above Fe) in our universe, and are important to shape isotopic abundances in the low mass region. In this talk, I will present recent measurements of radiative neutron capture and neutron-induced charged particle reactions relevant in astrophysics at the CERN n_TOF Facility, and future opportunities to address key open questions in the field.

Poster Pitch 1 Alexandru. N. State Aman Gandhi Cosmina Nedelcu Daniel-Grigore Chelaru Hiroki Kawashimo Iryna Timchenko Itay Goldberg Jan Butz Midhun C. V. Prabhat Mishra Sakshi Gautam Sangeeta Dhuri Simon Vincent State Dana Teodora Sebe Vincent Lelasseux Xiao Zhang

Probing Stellar Evolution and Fundamental Symmetries via Indirect Methods: The Trojan Horse Approach

• A. Tumino (Laboratori Nazionali del Sud INFN, Catania, Italy)

This contribution highlights the use of indirect nuclear techniques, specifically the Trojan Horse Method (THM) [1,2], to determine stellar reaction rates that are otherwise inaccessible via direct measurements. The presentation will focus on recent results regarding carbon burning fusion ($^{12}$C+$^{12}$C and $^{12}$C+$^{16}$O), where the study of alpha and proton evaporation channels has revealed resonant structures that significantly enhance reaction rates at astrophysical temperatures. Furthermore, I will discuss the interdisciplinary application of these methods to probe the charge symmetry breaking of nuclear force through the measurement of the Coulomb-free proton-proton scattering length. These results underscore the power of indirect approaches in addressing both the mechanisms of stellar evolution and the underlying properties of nuclear interactions. [1] A. Tumino, C.A. Bertulani, M. La Cognata, L. Lamia, R.G. Pizzone, S. Romano and S. Typel, Annual Review of Nuclear and Particle Science 71, (2021) 033642 [2] A. Tumino et al., Progress in Particle and Nuclear Physics 143 (2025) 104164

Nuclear Astrophysics deep underground: the LUNA experiment

• Rosanna Depalo (Università degli Studi di Milano and INFN Milano)

The cross sections of nuclear reactions relevant for astrophysics are crucial ingredients to understand the synthesis of the elements, starting from the Big Bang, as well as stellar evolution. In astrophysical environments, nuclear reactions take place at energies well below the Coulomb barrier. As a result, their cross sections are often too small to be measured in laboratories on the Earth’s surface, where the signal would be overwhelmed by the cosmic-ray induced background. An effective way to suppress the cosmic-ray induced background is to perform experiments in underground laboratories. LUNA (Laboratory for Underground Nuclear Astrophysics), located at Gran Sasso National Laboratories (Italy), has paved the way for underground nuclear astrophysics. Over the years, the LUNA collaboration has studied many crucial reactions involved in stellar evolution and Big Bang Nucleosynthesis. The presentation will provide an update on the latest results and future perspectives of the LUNA experiment.

p + 11B fusion measurement with ELISSA

• Kabita Kundalia (ELI-NP /IFIN-HH)

The reaction $^{11}$B$(p,\alpha)\alpha\alpha$ is the primary mechanism for $^{11}$B burning in the stellar environment, which makes it a reaction of interest in nuclear astrophysics. Additionally, this fusion reaction is also relevant in nuclear fusion reactor development, promising clean energy and relatively simplified reactor engineering. The present work focuses on the cross section measurement of this fusion reaction with proton energies ranging from 300 keV to 2600 keV on the $^{11}$B target using the Extreme Light Infrastructure Silicon Strip Array (ELISSA). In the experimental set up we use two rings of 10 resistive Silicon Strip each in cylindrical configuration and double sided strip detectors in the back angles, covering an overall range of angles from 40$^{\circ}$ - 165$^{\circ}$. We observe the reaction populating the $\alpha_0$ and $\alpha_1$ channels from the sequential decay of $^{12}$C. The precise measurement of the total cross section of these channels can resolve the discrepancies in the existing measurements and can be further used as reliable input for future applications.

Low-energy investigation of 24Mg(p,g)25Al reaction at LUNA (YRP)

• Giovanni Saturno (Gran Sasso Science Institute / INFN-LNGS)

The ${}^{24}\mathrm{Mg}(p,\gamma){}^{25}\mathrm{Al}$ reaction plays a key role in the Mg–Al cycle, influencing the nucleosynthesis of intermediate-mass nuclei, the chemical evolution of asymptotic giant branch stars, and the production of radioactive ${}^{26}\mathrm{Al}$. Despite its astrophysical importance, the reaction rate at stellar energies remains poorly constrained due to the extremely low cross sections within the sub-resonant Gamow window. This work presents an experimental study of the ${}^{24}\mathrm{Mg}(p,\gamma){}^{25}\mathrm{Al}$ reaction carried out at the INFN Laboratory of Gran Sasso within the LUNA collaboration. The underground environment provides a strong suppression of cosmic-ray induced background, enabling high-sensitivity measurements. However, beam-induced background from target contaminants remains a major source of systematic uncertainty, often exceeding the signal of interest by several orders of magnitude. For this reason, particular attention has been devoted to the production and characterization of high-purity magnesium targets. Magnesium thin films were prepared using thermal evaporation and magnetron sputtering techniques, combined with different backing materials to optimize both purity and stability. The targets were characterized through Rutherford Backscattering Spectrometry and Nuclear Reaction Analysis, allowing precise determination of thickness, stoichiometry, and impurity depth profiles. We focus our investigation on the experimentally accessible energy range between 200 and 400 keV, which includes two narrow resonances and a direct-capture component. Reaction $\gamma$-rays were acquired using two different setups: a high-efficiency $4\pi$ BGO detector and an HPGe detector. A coincidence-based analysis technique was developed for the first setup, exploiting detector segmentation together with multiplicity and energy-gating conditions to enhance sensitivity to weak capture signals. This method was validated on the $E_p = 223$ keV resonance and subsequently applied to the off-resonance data, improving the determination of the cross section in the region where direct capture is dominant. For the second, the excellent energy resolution of the detector and the stability of the LUNA - 400 accelerator, allowed an improved determination of the low energy resonance energy and provided an independent study of the off-resonance cross section. In this talk, we present the results of both analysis, which demonstrate the effectiveness of combining high-purity targets, underground measurements, and advanced detection techniques for low-energy radiative-capture studies. We also present our stellar rate evaluations with uncertainties, performed with a Monte Carlo R-matrix analysis.

The fluorine conundrum in stars

• Marco La Cognata (INFN-LNS)

The amount of fluorine in stars is a crucial indicator of the internal physical conditions and of the processes taking place within them, such as extra mixing in asymptotic giant branch stars. Also, it is a branching point in proton induced nucleosynthesis, since its proton radiative capture may lead to the synthesis of heavier nuclei (such as Ca in early stars). Recent extrapolated findings on the 19F(p,αγ)16O and 19F(p,γ)20Ne fluorine-destruction channels by the JUNA collaboration indicated a rise in the astrophysical factor by several orders of magnitude below about 100 keV, significantly affecting our comprehension of stellar evolution and nucleosynthesis. Utilizing the Trojan Horse Method (THM), we have indirectly measured the 19F(p,αγ)16O cross section, fully covering astrophysical energies without requiring extrapolations (and with no electron screening enhancement). The strength of the 11-keV resonance was determined, revealing a considerable decrease in the reaction rate compared to earlier studies. The THM results on the αγ channel were also used to rescale the 19F(p,γ)20Ne astrophysical factor, with similar conclusions. Our analysis of its astrophysical significance suggests that this measurement challenges existing models of fluorine and heavier element abundances, reopening unresolved questions in the field, in particular in the case of early stars. Results are discussed in detail in Xu et al., Phys. Rev. Lett. 135, 182701 (2025).

New direct measurement of 12C+12C reaction near astrophysical energies at LUNA

• DIPALI BASAK (Laboratori Nazionali del Gran Sasso - INFN)

The $^{12}$C+$^{12}$C fusion reaction is an important pathway for the synthesis of elements with mass A$\geq$20 and for the later stages of stellar evolution. Information on cross-section of $^{12}$C+$^{12}$C reaction below E$_{cm}$ = 2.2 MeV is sparse and previous measurements reported by different groups exhibit substantial inconsistencies. A new measurement of this reaction has been performed directly via $\gamma$-rays detection within the LUNA experiment at the Bellotti Ion Beam Facility (BIBF), located in the deep underground laboratory of Gran Sasso National Laboratory. The background intrinsic to the detection methods causes a significant uncertainty in the measured cross-section at sub barrier energies. Therefore, background reduction using both active and passive shielding is necessary. In this campaign, the $\gamma$-rays were detected using a high-efficiency (150$\%$), high-resolution HPGe detector, paired with two large-volume NaI(Tl) annulus detectors, each divided into eight sections. The entire detection system is enclosed by passive shielding consisting of 25 cm of lead and 1 cm of copper. Here, we present our detailed detector characterization leading to a major reduction in target contamination. The experimental spectra were benchmarked against GEANT4 simulations, validating the detection setup and enabling us to present the first preliminary results of our direct reaction cross-section measurements.

New measurements of the 15N(α, γ)19F reaction at the Felsenkeller laboratory (YRP)

• Peter Hempel

One of the main contributions to the production of 19F is the 15N(α, γ)19F re- action, which occurs during the Helium burning phase in different astrophysical sites including AGB stars and Wolf Rayet stars. However the reaction rate at astrophysical energies is still poorly known. Here we report on a measurement of different resonances of the 15N(α, γ)19F re- action in the 0.5 - 1.5 MeV center-of-mass energy range, performed at the 5 MV Felsenkeller shallow-underground accelerator in Dresden, using tantalum nitride solid targets enriched in 15N, multiple HPGe-detectors and the new FeliciTAS 4π BGO γ-ray calorimeter

Big Bang Nucleosynthesis and The Cosmological Lithium Problem

• ani aprahamian (University of Notre Dame)

Over 99.9 percent of the baryonic mass of all the universe comes from the nuclei at the center of every atom. These nuclei are made of protons and neutrons that themselves formed a few microseconds after the big bang as the primordial quark-gluon plasma cooled and condensed. Approximately three minutes after the Big Bang, the abundances of the primordial elements in the universe include protons, deuterons, 3He, 4He, and trace amounts of lithium and beryllium. Theoretical predictions for the primordial abundances of these elements are in good agreement and consistent with observations of the abundances for deuterons, 3He, and 4He but not for lithium. The lithium abundance predictions are 2.5 - 3.0 times higher than observed values even when the correct baryon-to-photon ratio of the Universe obtained from anisotropies of cosmic microwave background radiation is included. This discrepancy between the predicted primordial abundance of lithium from Big Bang nucleosynthesis and the observed abundances is known as the cosmological Li problem. We propose tritium induced reactions as potential avenues for impacting the resulting Li abundances. Tritium is neutron-rich and has a half-life of 12.323 years. Tritium was not thought to have any significant impact on long-lived stellar scenarios and therefore neglected. I will discuss some potential paths to reduce the Li abundance. Tritium reactions may also be important in the deaths of stars with core-collapse supernovae, or neutron star mergers where the synthesized elements are disassociated to be synthesized again.

Alpha-induced reactions on 10B at LUNA: First results for primordial nucleosynthesis

• Marialuisa Aliotta (University of Edinburgh)

The onset of the CNO cycle in Population III stars requires the production of carbon, nitrogen, and oxygen nuclei in an environment initially devoid of metals. Among the proposed mechanisms, α-induced reactions on light nuclei such as boron and lithium may provide a pathway for the synthesis of CNO material from primordial hydrogen and helium [1]. The corresponding reaction rates remain poorly constrained at astrophysical energies, primarily due to the experimental challenges associated with measuring very low yields and the presence of resonant structures near threshold [2]. Improved experimental data in the relevant energy range are therefore essential to better constrain these processes. Within the ERC NUCLEAR project [3], we are investigating alpha-induced reactions at the Laboratory for Underground Nuclear Astrophysics (LUNA) at LNGS (Italy), in collaboration with the University of Notre Dame (USA), taking advantage of the ultra-low background conditions provided by the underground environment. Measurements are being performed using the 400 kV accelerator [4], focusing on 10B in the astrophysically relevant energy region. In this contribution, I will present the status of the experimental campaigns together with first yield measurements and ongoing analysis efforts. This work is supported, in part, by the ERC NUCLEAR project (UKRI grant EP/Z534626/1). [1] M. Wiescher et al. Eur. Phys. J. A (2021) 57:24 [2] A. Gula et al. Phys. Rev. C 107 (2023) 025805 [3] NUclear CLustering Effects in Astrophysical Reactions https://www.erc-nuclear.uk [4] A. Formicola et al. Nucl. Instr. Meth. A 507 (2003) 609-616

Primary 4N production in zero metallicity massive stars (YRP)

• Agnese Falla

Population III (Pop III) stars are the first generation of stars formed in the Universe from the collapse of pristine gas left behind by the Big Bang, driving the very first cosmic chemical enrichment. Recent observations from the James Webb Space Telescope (JWST) have revealed unexpectedly high N/O ratios at high redshifts ($z > 3$), raising a major challenge for standard Galactic Chemical Evolution (GCE) models, which often fail to reproduce these elevated nitrogen abundances without invoking extreme or fine-tuned scenarios. Since Pop III stars are capable of producing primary $^{14}\mathrm{N}$ via internal mixing mechanisms, they represent a key candidate for polluting the nitrogen enhanced Interstellar Medium (ISM) observed at high redshift. With this scenario in mind, I computed a new grid of non-rotating and rotating Pop III stellar models using the FRANEC code, followed by core collapse supernova explosions calculated with the HYPERION code. In this talk, I will focus specifically on the nitrogen production and yields, presenting the key mechanisms driving primary $^{14}\mathrm{N}$ production, which have crucial implications for interpreting the anomalous N/O ratios observed in early galaxies.

Bayesian-Refined R-Matrix Study of 13C(alpha,n)16O and Its Influence on Stellar s-Process Nucleosynthesis (YRP)

• taoyu jiao (HUN-REN CSFK)

The $^{13}$C($\alpha,$n$)^{16}$O reaction is the primary neutron source for the stellar slow neutron-capture (s-) process and also plays an important role in intermediate (i-) process nucleosynthesis. Due to the extremely small cross sections at astrophysical energies and the overwhelming cosmic-ray–induced background in surface laboratories, direct measurements remain highly challenging. Recent underground measurements performed by the Jinping Underground Nuclear Astrophysics collaboration (JUNA) and the Laboratory for Underground Nuclear Astrophysics collaborations (LUNA) covered nearly the entire i-process Gamow window and reached the edge of the s-process Gamow window. These measurements, together with newly available differential cross-section measurements from the University of Notre Dame, substantially reduced the experimental uncertainty in the astrophysical energy region and provided new constraints for reaction-rate evaluations. In this work, we present a comprehensive Bayesian-refined R-matrix analysis of the $^{13}$C($\alpha,$n$)^{16}$O reaction by simultaneously incorporating all currently available experimental data. Particular attention is given to the subthreshold resonances, whose interference pattern and reduced width strongly influence the low-energy extrapolation of the reaction cross section. Based on the updated reaction rate, we further investigate its astrophysical impact through asymptotic giant branch (AGB) stellar models by comparing nucleosynthesis predictions obtained with different reaction rates.

New measurement of the 146Nd(n,g) cross section via time-of-flight and activation (YRP)

• Bernardo Bernardino Gameiro (Instituto de Física Corpuscular (IFIC))

The s-process is responsible for the synthesis of approximately half of the elements heavier than ⁵⁶Fe, and its nucleosynthesis yields in AGB and massive stars determine the isotopic abundances of heavy elements in the stellar systems. The most precise constraints available for the Nd isotopes are provided by isotopic ratio measurements from presolar stardust silicon carbide (SiC) grains. These observations are in persistent disagreement with stellar nucleosynthesis model predictions, which can be resolved if an enhancement of ~15% in the ¹⁴⁶Nd neutron capture cross section is assumed at the stellar temperature kT = 8 keV [1]. The existing experimental database for ¹⁴⁶Nd(n,γ) is severely limited: the reference data by Bao et al. [2] relies on a single measurement by Wisshak [3] restricted to the unresolved resonance region (URR) and in tension with other available data, while no time-of-flight measurement of the resolved resonance region (RRR) exists. The s-process branching at ¹⁴⁷Nd is governed by the competition between neutron capture and β-decay, making the ¹⁴⁷Nd half-life a key nuclear input. A discrepancy exists in the literature between the long-standing reference value (10.98 d, Baba 1971 [4]) and a more recent measurement (11.26 d, Broderick 2019 [5]), with no consensus established. This uncertainty directly propagates into the predicted s-process isotopic ratios and limits the astrophysical interpretation of new cross section data. To address these challenges, a comprehensive multi-facility experimental campaign has been undertaken combining time-of-flight and activation techniques. High-resolution TOF measurements at EAR2-n_TOF [6] provide, for the first time, resonance-resolved ¹⁴⁶Nd(n,γ) data up to ~5 keV and, possibly, the average neutron capture cross section in the URR up to 100 keV. Complementary neutron activation measurements at the HiSPANoS facility at CNA (Seville) [7], exploiting the well-characterised quasi-stellar kT = 25 keV spectrum from the ⁷Li(p,n) reaction, yield a direct MACS determination sensitive to the URR. A second activation campaign at the NEAR station at n_TOF [8], which provides access to the integral cross section in different energy ranges, completes the dataset. In parallel, a dedicated measurement of the ¹⁴⁷Nd half-life has been performed via neutron activation and HPGe γ-spectrometry. This contribution presents preliminary results from this campaign, including the ¹⁴⁶Nd capture yield, the first experimental MACS values from activation, and a new ¹⁴⁷Nd half-life determination. The combined astrophysical impact on the s-process branching of ¹⁴⁷Nd and on the reconciliation with presolar SiC grain observations will be discussed. [1] T. R. Ireland et al., Geochimica et Cosmochimica Acta 221, 200-218 (2018) [2] Z.Y. Bao et al., Atomic Data Nucl. Data Tables 76, 70 (2000) [3] K. Wisshak et al., Phys. Rev. C 57, 391 (1998) [4] S. Baba et al., J. Inorg. Nucl. Chem. 33, 589 (1971) [5] K. Broderick et al., Appl. Radiat. Isot. 144, 54 (2019) [6] C. Weiss et al., Nucl. Inst. Methods A, 799, 90-98 (2015) [7] M.A. Millán-Callado et al., Radiation Physics and Chemistry 217 (2024) [8] N. Patronis et al., arXiv:2209.04443 (2022)

Poster Pitch 2 Adrian Rotaru Alexander Holas Alexandra Spiridon Ana Lupoae Andreea Gavrilescu Christina Fakiola Enakshi Senapati Guruprasad Yagadevan Jyothish Kaiprath Peter Hempel Rahul Raphael Hirschi Ryota Hatami Sara Montella Sara Rebeca Ban Sohichiroh Aogaki Wan Aishah Wan Harun Zoltán Kóródi Zsolt Matyus Eliana Masha

Poster presentation

Illuminating heavy element production using MeV gamma-rays and metal-poor stars

• Nichole Vassh (TRIUMF, Canada)

Fingerprints of the properties of exotic nuclei on nucleosynthesis observables have been used for decades to frame our picture of how the heaviest elements are produced. The abundance of elements in our Sun and metal-poor stars hints at multiple neutron capture nucleosynthesis processes, the slow (s), intermediate (i) and rapid (r) neutron capture processes. Not only are the site(s) of the r and i processes under active study, but open questions remain regarding how much each of these contributed to the overall enrichment of stars such as our Sun. In particular, the r process synthesizes exotic and unstable nuclei that have yet to be probed in terrestrial experiments, implying r-process studies must consider nuclear physics uncertainties in the interpretation of observables. To move towards a systematic and modern approach, we explore applications of machine learning to decipher metal-poor star abundance patterns and highlight recent results. MeV gamma rays are also an exciting opportunity to pin down the element production of r-process events and hunt for nearby remnants. I will present recent work demonstrating the utility of MeV gamma rays from r-process nuclei (e.g. Rh-106 and Tl-208) that could be used to indicate whether an event reached the heaviest r-process isotopes (A>130) or solely produced a weak r process (A<130). I will also discuss the opportunity to refine our understanding of observables through future measurements at radioactive isotope beam facilities and show how recently reported nuclear masses from cutting-edge ab initio nuclear theory impact our picture for the abundance of key elements (e.g. gold) in neutron star mergers. Novel, interdisciplinary work at the intersection of observation, experiment, theory, and computational science are key to carving out the new ideas and tools needed to tease out the big picture of heavy element origins.

Probing Heavy Element Nucleosynthesis Through Electromagnetic Observations

• Gabriel Martinez-Pinedo (GSI Helmholtzzentrum für Schwerionenforschung, Institut für Kernphysik (Theoriezentrum), Technische Universität Darmstadt)

Half of the elements heavier than iron are produced by a sequence of neutron captures, beta-decays and fission known as r-process. It requires an astrophysical site that ejects material with extreme neutron rich conditions. Once the r-process ends, the radioactive decay of the freshly synthesized material is able to power an electromagnetic transient with a typical intrinsic luminosity. Such kilonova was observed for the first time following the gravitational signal GW170817 originating from a merger of two neutron stars. This observation answered a long lasting question in nuclear astrophysics related to the astrophysical site of the r-process. In this talk, I will summarize our current understanding of r-process nucleosynthesis. I will also illustrate the unique opportunities offered by kilonova observations to learn about the in-situ operation of the r-process and the properties of matter at extreme conditions. Achieving these objectives, requires to address fundamental challenges in astrophysical modeling, the physics of neutron-rich nuclei and high density matter, and the atomic opacities of r-process elements required for kilonova radiative transfer models.

Revisiting r-process signatures with 3D non-LTE stellar spectroscopy (YRP)

• Mila Racca (Stockholm University)

The rapid neutron-capture process (r-process) is responsible for producing roughly half of the elements heavier than iron, including Ag, Au, Th, and U. Despite its fundamental role in cosmic chemical evolution, the astrophysical sites and physical conditions of the r-process remain poorly constrained. Metal-poor, r-process enhanced stars provide unique laboratories to address this problem, as their surface abundances preserve the chemical signature of the gas from which they formed. However, extracting precise and reliable abundance patterns from high-resolution spectra critically depends on the accuracy of the underlying atmospheric models and spectral analysis techniques. In this contribution, I present a new high-precision abundance analysis of the very metal-poor ([Fe/H]~-3.5) and r-process enhanced star SMSS J200322.54−114203.3, previously studied in 1D LTE by Yong et al. (2021). Our analysis is based on high-resolution UVES spectroscopy, combined with state-of-the-art 3D hydrodynamical model atmospheres and (non-)local thermodynamic equilibrium (NLTE/LTE) radiative transfer. We derive full 3D NLTE abundances for Na, Mg, Al, Si, Ca, Cu, Ag, and Ba, and 3D LTE abundances for additional neutron-capture elements. This homogeneous approach allows us to directly quantify the systematic biases introduced by commonly adopted 1D LTE methods. Our preliminary results reveal large and element-dependent discrepancies with respect to previous 1D LTE studies, with 3D NLTE corrections reaching up to ~1 dex for some key elements, most notably aluminium and magnesium. These differences propagate into the elemental ratios that are widely used to compare observed stars with theoretical nucleosynthetic yields. In particular, the 1D LTE abundances reported by Yong et al. were found to correlate well with magnetorotational hypernova yield models. Our revised 3D (NLTE/LTE) abundance pattern substantially alters several of these key ratios and therefore challenges this apparent agreement, with important consequences for identifying the physical site of the r-process event and for tracing its contribution to the early chemical evolution of the Milky Way.

Low energy measurement of the 86Kr(α,n)89Sr and 86Kr(p,n)86Rb reactions for studying the weak r-process nucleosynthesis (YRP)

• Sándor Kovács (HUN-REN Institute for Nuclear Research (ATOMKI))

Nucleosynthesis above the iron region mainly proceeds via successive neutron capture processes, such as the s- and r-processes. However, in the case of neutrino-driven ejecta from a core-collapse supernova, nucleosynthesis runs relatively close to the valley of stability, hence it proceeds mainly via (α,n) and (p,n) reactions towards higher mass numbers [1]. Sensitivity studies have shown that (α,n) reaction uncertainties can be up to an order of magnitude, mainly due to differences in α-nucleus optical model (αOM) potentials [2]. This nuclear uncertainty significantly impacts network calculations and calculated abundances [3,4]. Therefore, substantial effort has been devoted to measuring key (α,n) reactions that influence the weak r-process, such as the $^{86}$Kr(α,n)$^{89}$Sr reaction. These measurements have also been used to justify the adoption of a new αOMP, ATOMKI-V2 [5]. However, our latest reaction network study suggests that the impact of (p,n) reaction uncertainties should not be so easily disregarded as has been done so far. During our measurement campaigns, we measured the cross sections in the Gamow window for both $^{86}$Kr(α,n) and $^{86}$Kr(p,n) reactions [6,7]. In this presentation, we will share details on our experimental results, the application of ATOMKI-V2, the significance of (p,n) reactions, and the astrophysical implications of our new data. [1] A. Arcones and F. Montes, ApJ, 731 5 (2011). [2] J. Pereira and F. Montes, Phys. Rev. C, 93 034611 (2016) [3] J. Bliss, A. Arcones, F. Montes, and J. Pereira, Phys. Rev. C, 101 055807 (2020) [4] A. Psaltis et al., ApJ, 935 27 (2022) [5] P. Mohr et al., Eur. Phys. J. A, 61 89 (2025) [6] G. G. Kiss et al., ApJ, 988 170 (2025) [7] S. R. Kovács, in preparation

Solar fusion reactions and LUNANOVA

• Daniel Bemmerer (Helmholtz-Zentrum Dresden-Rossendorf)

Our Sun burns hydrogen through the proton-proton cycles and, with a ssmall contribution, also by the carbon-nitrogen-oxygen cycle. These processes can be studied by their neutrino signatures. Whereas current solar neutrino detectors have delivered highly precise data for the solar Be-7 and B-8 neutrino fluxes, the underlying nuclear rates are significantly less well known. The ERC Synergy Grant LUNANOVA aims to correct this, with dedicated experiments deep underground at Gran Sasso, shallow underground at Felsenkeller, and at several overground facilities. These upcoming new data will be used to compute a new solar model.

Laser-Driven Nuclear Astrophysics

• D. Lattuada (INFN-LNS & Dipartimento di Ingegneria e Architettura, Università degli Studi “Kore”, Enna, Italy)

High-power, short-pulse lasers are opening a complementary route to classical accelerator techniques for studying nuclear reactions at energies relevant to astrophysics. By driving interactions with molecular-cluster jets, lasers can generate transient, high-density plasmas where fusion proceeds in partially ionized matter and under strongly time-dependent conditions. This offers a unique opportunity to investigate how plasma effects—such as plasma screening, collective fields, and non-thermal ion distributions—may modify effective reaction rates compared to “cold-target” measurements, and to benchmark the assumptions used in stellar and primordial nucleosynthesis models. In this invited talk, I will review the methodology and recent progress of laser-driven nuclear astrophysics experiments, with emphasis on cluster-based platforms. I will discuss how ion energy spectra and fusion-product yields can be measured simultaneously and combined to infer an effective reactivity in the plasma. Particular attention will be given to diagnostic strategies for low-energy ions and fusion products, including Thomson parabola spectrometers, ion time-of-flight detectors (CVD diamond), fast neutron scintillators, and optical plasma diagnostics. Results and lessons learned from recent campaigns on cryogenic deuterium and deuterated-methane targets will be presented, highlighting key experimental systematics such as energy-loss effects in the target and the impact of repetition-rate constraints. Finally, I will outline the roadmap toward next-generation measurements at facilities such as ELI-NP. There, controlled scans of target thermodynamics and focusing geometry (beam waist and Rayleigh length), together with high-contrast sub-picosecond pulses and advanced cryogenic cluster sources, will enable systematic optimization of laser–target coupling and fusion observables. The perspective is to establish a reproducible experimental framework that bridges nuclear astrophysics and high-energy-density plasma physics, providing benchmark data for plasma-modified reaction rates and charged-particle observables relevant to nucleosynthesis.

Experimentally constraining neutron capture rates for the r process

• Dennis Muecher (University of Cologne)

Neutron capture rates during the freeze-out phase of the astrophysical r process critically shape the final abundance distribution of heavy elements. For neutron-rich nuclei relevant to the r process, these rates remain largely unconstrained — direct measurements are experimentally inaccessible, and theoretical descriptions carry substantial uncertainties. In this contribution we present results from two experiments using state-of-the-art radioactive ion beam facilities and equipment. At the CARIBU facility at Argonne National Laboratory, we applied the $\beta$-Oslo technique combined with the newly developed "Shape method" to constrain nuclear level densities of neutron-rich Cs isotopes northeast of $^{132}$Sn. These results allow us to critically assess the validity of the Hauser-Feshbach statistical model in this region. We find that along the N = 86 isotone chain, declining nuclear level densities shift the capture mechanism toward a regime dominated by individual resonances, with rates potentially exceeding Hauser-Feshbach predictions by up to two orders of magnitude for the most exotic species. Our measurements demonstrate that we are experimentally approaching the limits of statistical behaviour. At the Facility for Rare Isotope Beams (FRIB), we targeted for the first time very neutron-rich nuclei southwest of $^{132}$Sn. near the N = 82 shell closure — a region identified as particularly sensitive for r-process freeze-out abundances, yet hitherto completely unexplored experimentally. Using the new SuN++ total absorption spectrometer, we obtained first spectra from these extremely neutron-rich nuclei and present a preliminary analysis of neutron capture rates below $^{132}$Sn.

DRHBc mass table and its impact on nucleosynthesis

• Jie Meng

From Nuclear Structure to Nuclear Astrophysics: Results from the ELIFANT Campaigns

• Asli Kusoglu (ELI-NP)

New ab initio constrained extended Skyrme equations of state for simulations of neutron stars, supernovae, and binary mergers

• Mikhail Beznogov

Context. Numerical simulations of core-collapse supernovae, mergers of binary neutron stars, and the formation of stellar black holes,using standard Skyrme interactions, have established clear correlations between the evolution of these processes, the characteristics of hot compact objects, as well as neutrino and gravitational wave signals, and the value of effective nucleon mass at the saturation density. However, the density dependence of the effective nucleon mass in these models does not align with the predictions of ab initio models with three-body forces. Aims. We investigated the thermal response for a set of extended Skyrme interactions that feature widely different density dependencies of the effective mass of nucleons. Methods. We studied thermal contributions to the energy density and pressure, along with several thermal coefficients, over wide domains of density, temperature, and isospin asymmetry that are relevant for the physics of hot compact objects. Results. For some of the effective interactions, the thermal pressure is negative at high densities. This results in hot compact stars supporting less mass before collapsing into a black hole compared to their cold counterparts. Moreover, the higher the temperature, the lower the maximum mass that the hot star can support.

Constraining neutron star parameters with kilonova spectra and signatures of hyperons

• Andreas Bauswein

The importance of GW170817 for equation of state constraints was immediately obvious after the event with various ideas that were proposed to learn about the properties of high-density matter. Recently, we proposed another method that leads to interesting constraints on the properties of neutron stars and the merger remnant. This is based on the consideration of the helium content in the ejecta. If helium is not very abundant as potentially suggested by a preliminary analysis of the kilonova spectra, the life time of the merger remnant is likely to be relatively short. This implies upper limits on the radii and the maximum mass of neutron stars. We will discuss a new signature in stellar parameters of isolated neutron stars that indicates the presence of hyperons in the stellar core as well as the impact of hyperons in neutron star mergers.

The Interior Physics of Neutron Stars

• Clara Dehman (University of Alicante)

Neutron stars are ultra-dense remnants of massive stellar cores, observable across the electromagnetic spectrum. Their emission reflects a complex interplay of magnetic, thermal, and structural processes operating under extreme conditions of density, temperature, and magnetic field strength that cannot be reproduced in terrestrial laboratories. Understanding isolated neutron stars therefore requires studying the physics of their interiors, where microphysical processes strongly influence both magnetic field evolution and stellar cooling. In this talk, I will introduce MATINS, a new open-access 3D code developed to model the coupled magneto-thermal evolution of isolated neutron stars. I will first discuss neutron star cooling, focusing on how observations of three faint, young neutron stars place new constraints on the nuclear equation of state. I will then turn to the physics governing magnetic field evolution, with particular emphasis on magnetars and the origin of their large-scale dipolar magnetic fields responsible for rapid spin-down. In this context, I will discuss the role of the chiral magnetic effect, arising from the chiral anomaly, which enables the mutual conversion between magnetic helicity and electron chiral asymmetry. Finally, in the last part of the talk, I will discuss finite-temperature equations of state relevant for describing hot compact objects, such as those encountered in the late stages of proto-neutron star evolution and in neutron star merger remnants.

A unified finite‑temperature equation of state with BSkG4: from nuclear structure to neutron star mergers

• Guilherme Grams (University of Potsdam)

Describing nuclear matter across the extreme range of densities, temperatures, and isospin asymmetries encountered in astrophysical environments remains a challenge. This is particularly critical for binary neutron star mergers, where both dense matter and clusterized low-density phases influence observable signals. In addition, r-process nucleosynthesis in the ejecta requires reliable nuclear structure inputs for thousands of neutron-rich nuclei. We build on the Brussels-Skyrme-on-a-Grid (BSkG) framework, which provides a unified and accurate description of nuclear structure and neutron star matter, including nuclear masses and fission barriers. Focusing on the BSkG4 parameterization [1], we construct a new finite-temperature equation of state (EoS) covering the range of conditions encountered in merger simulations. At sub-saturation densities, we describe inhomogeneous matter within a temperature-dependent extended Thomas-Fermi (TETF) approach [2], enabling a consistent semi-classical treatment of nuclei embedded in a nucleon fluid. This approach captures the composition and thermodynamics of clusterized matter in an efficient and accurate framework. We implement the resulting EoS in numerical-relativity simulations of binary neutron star mergers using the BAM code [3] and present first exploratory results. We discuss the impact of the new microphysics on the properties of the ejecta and related observables, including neutrino emission and kilonova signals. These results illustrate the role of a consistent nuclear physics description in multi-messenger astrophysics. [1] G. Grams, N. Shchechilin, A. Sanchez-Fernandez, W. Ryssens, N. Chamel, and S. Goriely. EPJA, 61, 35, (2025). [2] G. Grams, N. Shchechilin, T. Diverrès, A. Fantina, N. Chamel, and F. Gulminelli. Universe 11, 6 (2025). [3] H. Gieg, F. Schianchi, M. Ujevic, and T. Dietrich, PRD 112, 023036 (2025).

Charged-current neutrino opacity within the relativistic Hartree-Fock framework for astrophysical simulations of core-collapse supernovae and binary neutron star mergers (YRP)

• Kamil Sokołowski (Wrocław University of Science and Technology)

Neutrinos and their weak interactions play a vital role in the physics of core-collapse supernovae and binary neutron star mergers. Their description within astrophysical simulations, including the weak rates, is of crucial importance for the prediction of accurate neutrino fluxes and spectra. In my talk, I will introduce the charged-current weak rates treating the nuclear component at the level of the relativistic Hartree-Fock approach, which features explicitly momentum-dependent neutron and proton self-energies. It is this latter aspect which results in large differences in the neutrino opacity in comparison to the commonly employed relativistic Hartree mean-field approach. I will further discuss the differences between Hartree and Hartree-Fock charged current weak rates and emphasise the potential impact in astrophysical simulations.

Probing explosive nucleosynthesis with radioactive beams

• Artemis Tsantiri (University of Regina)

Explosive astrophysical environments, such as X-ray bursts, novae and supernovae govern nucleosynthesis on the proton-rich side of the valley of stability. In these sites, nucleosynthesis proceeds mainly through p- and α- induced reactions, as well as photodisintegration reactions that push the nuclear flux away from the valley of stability. Modeling these environments requires detailed knowledge of nuclear properties and reaction rates for the nuclei involved. To address this need, direct measurements in the astrophysically relevant Gamow window with radioactive beams are essential. In this talk, I will present two radioactive beam experiments for explosive nucleosynthesis. In the lighter-mass region, I will discuss one of the main breakout pathways from the hotCNO cycle towards explosive burning and the rp process, the $^{14}$O(α,p)$^{17}$F reaction. At typical burst temperatures, this reaction proceeds predominantly through a 6.15 MeV resonant state in $^{18}$Ne, that can decay through p, α or possibly 2p emission. Using the Active Target and Time Projection Chamber (ACTAR TPC) at TRIUMF, the 6.15 MeV resonance was populated through inelastic proton scattering on a radioactive $^{17}$F beam. This measurement aims to provide branching ratios between the 2p, p, and α decay channels by observing all particles in the final state. Moving on towards the heavy elements and the astrophysical γ process, I will present the first measurement of the $^{73}$As(p,γ)$^{74}$Se reaction, one of the main destruction mechanisms of the lightest p nucleus $^{74}$Se. The measurement was performed using a radioactive $^{73}$As beam with the Summing NaI (SuN) detector at the Facility for Rare Isotope Beams. Along with the total cross-section measurement, the impact of the extracted reaction rate in the production of $^{74}$Se in Type II supernovae will be presented.

Low-Energy Nuclear Reactions with Stored and Cooled Radioactive Beams

• Jan Glorius (GSI)

In the past decade, research into low-energy nuclear reactions has entered a new era in heavy ion storage rings. At the GSI rings ESR and CRYRING we are now able to conduct reaction cross section measurements with decelerated radioactive beams. In this talk I will give an overview of the different experimental campaignes that address astrophysical problems in this context. One of these initiatives is the proton-capture campaign in the ESR, which aims to directly measure proton-induced reactions of key importance for explosive nucleosynthesis. In the latest experiment, we successfully applied this technique to a radioactive beam for the first time. Another project is CARME, a setup that has recently been installed and commissioned in CRYRING. This versatile array of Si-detectors surrounding the internal gas target enables a wide range of low-energy studies with radioactive beams to be pursued. Recent results and developments as well as future plans within those projects will be discussed.

Experimental study of gamma-induced charged particle emission from 112Sn for the p-process (YRP)

• Teodora Petruse (Extrem Light Infrastructure - Nuclear Physics / IFIN-HH)

The origin of the rare proton-rich p-nuclei remains an open question in nuclear astrophysics. Since they are not efficiently produced by the s- and r-processes, they are thought to form mainly through photodisintegration of heavier seed nuclei in explosive stellar environments. A key uncertainty in p-process models comes from poorly constrained reaction rates. Since experimental data are missing for many relevant reactions, these rates often rely on Hauser-Feshbach calculations, which can vary significantly, especially for charged particle emission channels. This work presents a study of $\gamma$-induced reactions on $^{112}$SnSn, focusing on the charged-particle emission channels $^{112}$Sn($\gamma$,p) and $^{112}$Sn($\gamma$,$\alpha$). The experiment was performed at the High Intensity Gamma-ray Source, HI$\gamma$S, using monoenergetic $\gamma$-ray beams. Emitted protons and alpha particles were measured with a highly segmented silicon detector array, providing information on their energies and angular distributions. The experiment aims to determine total and partial photodisintegration cross sections for 112Sn in the energy region relevant to the p-process. These data will help constrain statistical model calculations and improve the reliability of reaction rates used in p-process nucleosynthesis models. In this presentation, the experimental setup, the identification of proton and alpha emission channels, the preliminary cross section results, and the relevance of the results for p-process reaction-rate calculations will be discussed.

Beyond Stability: a-scattering with exotic heavy nuclei for a-nuclear potential constrainment (YRP)

• Francisco Geraldes Barba (LIP - Laboratory of Instrumentation and Experimental Particle Physics)

The production of heavy elements in the universe is mainly dominated by neutron capture processes. However, some of the nuclei cannot be produced via this path. It is believed that one of the processes that produces heavy p-nuclei is governed by photodisintegration of s-process seed nuclei via ($\gamma$,n), ($\gamma$,p) and ($\gamma$,$\alpha$) reactions. Systematic studies have shown that one of the main sources of uncertainty for this process is the $\alpha$-nuclear potential in exotic nuclei [1,2], which can be studied through the measurement of elastic scattering differential cross-sections at energies around the Coulomb Barrier. I will present the first ever measured differential cross-sections of elastic scattered $\alpha$ particles off exotic nuclei. The experiment was performed at the HIE-ISOLDE facility at CERN profiting from the use of newly developed Si films with high $^4$He concentrations [3] to scatter exotic beams of $^{108,109,110}$Sn and the stable $^{112}$Sn beam produced at ISOLDE. Following the astrophysical motivation for the measurement, I will present details on the performed experiment and a proof-of-concept comparison with the previous measurement on the stable isotope $^{112}$Sn [4], concluding with the current status of the analysis of the $\alpha$-scattering of exotic nuclei. This measurement opens the possibility to measure $\alpha$-nuclear potentials in exotic proton-rich nuclei, contributing to the reduction of uncertainties in nuclear network calculation studies. References: [1] A. Simon, et al. J. Phys. G 44, 064006 (2017) [2] W. Rapp, et al. Astrophys. J. 653, 474 (2006). [3] V. Godinho, et al. ACS Omega 1(6), 1229 (2016). [4] D.Galaviz, et. al. Phys.Rev.C 71 065802 (2005)

n-capture in inverse kinematics

• Rene Reifarth (LANL)

Virtually all of the isotopes heavier than iron would not exist without neutron-induced reactions. Despite there importance in many different astrophysical scenarios, there are almost no direct measurements for isotopes with half-lives shorter than a few years. A radically new approach is necessary to overcome this constraint. Ion storage rings offer unprecedented possibilities to investigate radioactive isotopes of astrophysical importance in inverse kinematics. During the last years, a series of pioneering experiments proofed the feasibility of this concept for the fusion of charged particles at the Experimental Storage Ring (ESR) at GSI. More recently, first feasibility studies of a free-neutron target have been performed successfully. A free-neutron target combined with an ion storage ring can bring the half-life limit for direct neutron-induced reactions down to fractions of a minute. I will review different astrophysical scenarios, status of current experiments as well as prospects of this new experimental endeavor.

Direct and indirect approaches for Nuclear Astrophysics: recent highlights from LUNA and the AGATA campaigns

• Jakub Skowronski (Università degli Studi di Padova and INFN Padova)

The Laboratory for Underground Nuclear Astrophysics (LUNA), located in the Gran Sasso National Laboratory, has been at the forefront of measuring key nuclear reactions at astrophysical energies for over three decades. The ultra-low background environment of the underground site, combined with high-current accelerators and efficient detection systems, has enabled LUNA to provide direct cross-section measurements of reactions critical to stellar evolution and Big Bang nucleosynthesis, often for the first time in or near the Gamow window. This talk will review recent highlights from the LUNA program, including ongoing campaigns with the 3.5 MV accelerator, and discuss the impact of direct underground measurements on our understanding of stellar nucleosynthesis. However, for certain reactions, indirect data are necessary to fully constrain the low-energy extrapolation. A prominent example is the $^{14}$N(p,γ)$^{15}$O reaction, the slowest process in the CNO cycle, whose S-factor at zero energy, S$_{114}$(0), directly governs the predicted CNO neutrino flux and carries implications for the solar metallicity problem. In such cases, lifetime measurements of bound states in the compound nucleus become essential to provide independent constraints on the R-matrix extrapolation. In the talk, the results from a novel event-by-event Doppler-shift attenuation method (DSAM) lifetime measurement of states in $^{15}$O, performed using the AGATA γ-ray tracking array, will be presented as well. The high position resolution and tracking capability of AGATA enable a new level of precision in extracting lifetimes relevant to the ground-state transition of $^{14}$N(p,γ)$^{15}$O. We discuss how these complementary data, combined with the existing body of direct measurements, lead to a refined determination of S$_{114}$(0) and its astrophysical implications.

Measurement of the 12C(alpha,gamma) reaction by measuring the Photodissociation of 16O; a New Tool for Nuclear Astrophysics

• Moshe Gai (University of Connecticut)

We developed a new method for measuring the cross section of capture reactions (that occur in stellar processes) by measuring the time reverse Photodissociation reaction occurring inside TPCs operating in gamma-beams. This measurement of the time reverse process is not an indirect measurement and certainly not a “surrogate measurement”. It relies on the well-recognized concept of Detailed Balance. We specifically discuss measurements of the $^{12}$C($\alpha,\gamma$) reaction by measuring the photodissociation of $^{16}$O contained in the CO$_2$ gas of the TPC; the $^{16}$O($\gamma,\alpha$)$^{12}$C reaction. Initial measurements were carried out using the UConn-TUNL-Weizmann-PTB optical readout TPC (O-TPC) [1] operating with 100 torr CO$_2(80\%)$ + N$_2(20\%)$ gas mixture, placed in the gamma beam of the HIgS/TUNL at Duke University. Using the O-TPC we demonstrated [2] the validity of our new method and bench marked it against world data, with the measured total reaction cross section that agrees with the world data. During 2021 the O-TPC was decommissioned and replaced by the Warsaw electronic readout TPC (eTPC) [3]. We will discuss the new readout technologies and the setup of the TPC detectors and report on new results obtained using the Warsaw eTPC [3] and the O-TPC operating with N$_2$O gas [4]. We report angular distribution measured with unprecedented accuracy [3-5]. Specifically, we measured the E1-E2 mixing phase angle (f12) of the $^{12}$C($\alpha,\gamma$) reaction, that for the first time agrees with the prediction of unitarity [6]. The material presented here is based on work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics grants Number DE-FG02-94ER40870. References $[1]$ M. Gai, M.W. Ahmed, S.C. Stave, W.R. Zimmerman, A. Breskin, B. Bromberger, R. Chechik, V. Dangendorf, Th. Delbar, R.H. France III, S.S. Henshaw, T.J. Kading, P.P. Martel, J.E.R. McDonald, P.-N. Seo, K. Tittelmeier, H.R. Weller and A.H. Young, Jour. Instr. 5, 12004 (2010). $[2]$ R. Smith, M. Gai, S.R. Stern, M.W. Ahmed, Nature Communications 12, 5920 (2021). $[3]$ M. Ćwiok, W. Dominik, A. Fijałkowska, M. Fila, Z. Janas, A. Kalinowski, K.Kierzkowski, M. Kuich, Ch. Mazzocchi, W. Okliński, M. Zaremba, M. Gai, D.K. Schweitzer, S.R. Stern, S. Finch, U. Friman-Gayer, S.R. Johnson, T. Kowalewski, D.L. Balabanski, C. Matei, A. Rotaru, K.C.Z. Haverson, R. Smith, R.A.M. Allen, M.R. Griffiths, S. Pirrie, and P.S.R Alcibia, EPJ Web Conf. 279, 04002 (2023). $[4]$ Kristian C.Z. Haverson, Robin Smith, Moshe Gai, Deran K. Schweitzer, Sarah R. Stern and Sean W. Finch, Communications Physics, 9, 27(2026).https://doi.org/10.1038/s42005-025-02458-7 $[5]$ Kristian C.Z. Haverson and Mikolaj Ćwiok et al., Submitted to Nature Communication, 2026. https://doi.org/10.21203/rs.3.rs-10181237/v1 $[6]$ Moshe Gai. Phys. Rev. C 88, 062801(R) (2013).

Surrogate reactions at the Experimental Storage Ring

• Guy Leckenby (Universite de Bordeaux, CNRS, LP2I Bordeaux, Gradignan 33170, France)

Neutron-induced reaction cross sections of short-lived nuclei are essential inputs to the astrophysical processes that produce elements heavier than iron. However, these cross sections are very difficult or impossible to measure due to the difficulty of producing and handling the necessary radioactive targets. The NECTAR project at the Experimental Storage Ring in GSI, Darmstadt demonstrates, for the first time, surrogate reactions in inverse kinematics at a heavy-ion storage ring. The method allows us to measure all the de-excitation probabilities of the same compound nucleus that is formed in the neutron-induced reaction, as a function of the excitation energy, and indirectly determine the aforementioned cross sections. In this contribution, I will present results from our first two demonstration experiments where we investigated the ($p,p'$), ($d,p$) and ($d,d'$) surrogate reactions on $^{208}$Pb and $^{238}$U beams. In these experiments, we achieved a significant breakthrough by measuring for the first time the fission, $\gamma$-ray, neutron and even two- and three neutron emission probabilities simultaneously. The measurement of all competing decay channels enables the precise determination of fundamental quantities, including fission barriers, particle transmission coefficients, $\gamma$-ray strength functions, and nuclear level densities that allow us to infer ($n,f$), ($n,\gamma$), ($n,n'$), ($n,2n$), and ($n,3n$) cross sections. I will also describe our future plans to use the storage ring to perform surrogate reactions on radioactive beams.

Progress towards direct measurement of neutron-induced reactions in inverse kinematics with the Neutron Target Demonstrator (YRP)

• Caroline Harrington (Air Force Institute of Technology)

Neutron-induced reactions play central roles in the study of stellar nucleosynthesis. The study of these reactions on rare isotopes has been hindered by short lifetimes, which rule out the standard approach of neutrons impinging on a fixed target. The future Neutron Target Facility at Los Alamos National Laboratory follows an inverse kinematics approach, combining a rare-isotope beam with a moderated spallation-neutron field to form a “neutron target.” Recent measurements validated the simulated energy and spatial distribution of the neutron flux within a graphite moderator. A proof-of-principle neutron-capture experiment with a stable $^{78}$Kr beam is planned. This work enables future measurements on short-lived nuclei providing strong constraints on nucleosynthesis models across the chart of nuclides.

PANDORA: A New Experimental Platform for Probing $\beta$ Decays in Stellar-Like Plasmas

• Eugenia Naselli (Centro Siciliano di Fisica Nucleare e Struttura della Materia and INFN-LNS)

The properties of radioactive nuclei embedded in hot, highly ionized plasmas play a fundamental role in stellar nucleosynthesis. In particular, the ionization state can profoundly modify beta-decay rates through the opening of additional decay channels, such as Bound-State Beta Decay (BSBD), experimentally observed in fully stripped ions stored in heavy-ion storage rings. These effects can alter the lifetime of selected radionuclides by several orders of magnitude, influencing key branching points along the s-process nucleosynthesis path. A major experimental challenge is the investigation of these phenomena under plasma conditions resembling stellar interiors, where ions coexist with free electrons over a broad distribution of charge states. Addressing this challenge is the primary scientific objective of PANDORA (Plasmas for Astrophysics, Nuclear Decays Observation and Radiation for Archaeometry), a new facility under construction at INFN-LNS. PANDORA will exploit a superconducting Electron Cyclotron Resonance magnetic trap to generate stable, magnetically confined plasmas with electron temperatures of several tens of keV and accurately controlled plasma parameters. Within this environment, the decay rates of selected radionuclides — including 94Nb, 176Lu, and 134Cs — will be measured during the first experimental phase (starting from late 2027), as a function of the plasma ionization conditions, providing the first laboratory investigation of beta decay in stellar-like, non-LTE plasmas. A list of more than 110 isotopes is ready for further and future measurements, including 7Be and other radionuclides relevant in astrophysical scenarios. Beyond its physics goals, PANDORA represents a novel experimental platform combining plasma production with advanced non-invasive diagnostics, including high-resolution X-ray spectroscopy, interferometry, polarimetry, and gamma-ray detection. These complementary techniques enable a comprehensive characterization of the plasma environment, allowing nuclear observables to be directly correlated with independently measured plasma parameters. They will also enable the investigation of plasma opacities under stellar-like conditions, providing valuable experimental benchmarks for the interpretation of kilonova light curves and the inference of r-process elemental abundances in the ejecta. This contribution will present the scientific motivations, experimental approach, and diagnostic capabilities that make PANDORA a unique tool for benchmarking models of weak interactions and radiative plasma properties under stellar-like conditions, thereby strengthening the connection between laboratory plasma physics and nuclear astrophysics.

Fusion Cross Section Measurements of 16C + 12,13C with Implications for X-Ray Superbursts (YRP)

• Valarie Milton (Louisiana State University)

Abstract: X-ray superbursts are powered by runaway thermonuclear burning deep inside the crust of a neutron star, for which the pycnonuclear fusion of neutron-rich isotopes is an important heat source. A major source of uncertainty in models of superbursts stems from nuclear cross sections for the fusion of neutron-rich isotopes, which cannot currently be measured. To help constrain astrophysical models, the $^{16}$C + $^{12,13}$C fusion reaction was measured at Argonne National Laboratory's ATLAS facility. A 220-MeV radioactive beam of 16C was produced by the RAISOR (RAdioactive Ion SeparatOR) facility and delivered with a rate of 1,200 pps and beam purity of 50-80%. The reactions were measured by MUSIC (MUlti-Sampling Ionization Chamber), an active target detector filled with methane or $^{13}$C-enriched methane gas at 400 Torr. The $^{16}$C + $^{12,13}$C cross sections were measured for EC.M. less than and approx. equal to 25 MeV. This is the most neutron-rich carbon fusion system that has been studied experimentally to date. The experimentally measured cross sections for these two fusion reactions and comparisons to current fusion models will be presented. This work is supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-AC02-06CH11357, grant No. DE-FG02-96ER40978, and grant No. DE-SC0026091. This research used resources of ANL's ATLAS facility, which is a DOE Office of Science User Facility.

Explosive nucleosynthesis in novae and X-ray bursts

• Jordi Jose (UPC Barcelona)

Novae and X-Ray Bursts are among the most important stellar explosions in our Galaxy. Classical novae are driven by thermonuclear explosions in the envelopes accumulated through mass transfer onto white dwarf stars in close binary systems. During these events, approximately $10^{-7}-10^{-4}$ M$_\odot$ of material enriched in CNO nuclei, and in some cases in intermediate-mass elements such as Ne, Na, Mg, and Al, are ejected into the interstellar medium. Infrared and ultraviolet observations have also confirmed dust formation in the expanding nova ejecta, raising the possibility that novae may contribute to the inventory of presolar grains found in meteorites. Recent work on the subclass of recurrent novae, including studies of T CrB and other well-known systems, has focused on characterizing their accretion histories and white-dwarf masses. In many recurrent novae, the accreting white dwarf is inferred to be close to the Chandrasekhar mass because of the observed short recurrence periods. Numerical simulations suggest that such systems may experience net white-dwarf mass growth, making at least some recurrent novae plausible progenitors of thermonuclear supernovae. X-ray bursts (XRBs) are another class of thermonuclear explosions that involve neutron stars rather than white dwarfs. These events constitute the most frequent type of thermonuclear stellar explosion in our Galaxy (the third, in terms of total energy output after novae and supernovae). To date, most of the efforts undertaken in the modeling of XRBs have relied on non-rotating, 1D hydrodynamic simulations. We will report on pioneering XRB models computed with different angular velocities (up to 80% of the critical value) and discuss the differences obtained in the lightcurves and in the associated nucleosynthesis with respect to non-rotating models. It is worth noting that, while all XRB hydro simulations performed to date report that ejection from a neutron star is unlikely, radiation-driven winds during photospheric radius expansion have been suggested to lead to the ejection of a tiny fraction of the accreted envelope. Here, we will report the results of the coupling of a non-relativistic, radiative wind model with a series of XRB hydrodynamic simulations, quantifying the expected contribution of XRBs to the Galactic abundances. This invited talk will review the current understanding of novae and XRB, with empasis on the explosion mechanisms, the main nuclear processes involved and their associated uncertainties. Particular attention will be devoted to the impact of nuclear reaction rates and weak interactions on abundance predictions and observational diagnostics.

Experimental studies of explosive nucleosynthesis in binary systems

• Nicholas de Sereville (IJCLab, France)

Type I X-ray bursts and classical novae are thermonuclear explosions occurring on the surface of accreting compact objects, neutron stars and white dwarfs, in close binary systems. Interpreting their observational signatures, including light curves for X-ray bursts and elemental and isotopic abundances for classical novae, requires precise knowledge of the underlying nuclear physics. I will review recent experimental advances critical to understanding nucleosynthesis and energy production in these explosive stellar environments, with a focus on key reaction rates involving proton-capture processes and hot-CNO cycle breakout reactions on unstable nuclei. I will discuss how these reactions directly impact X-ray burst light curves and the abundance yields observed in nova ejecta.

Probing explosive nucleosynthesis underground: recent LUNA measurements at the Bellotti IBF

• Federico Ferraro (INFN-LNGS)

For over thirty years the LUNA (Laboratory for Underground Nuclear Astrophysics) collaboration has exploited the ultra-low background of the Gran Sasso National Laboratory (LNGS) to measure key nuclear reactions directly at the energies of astrophysical interest. With the 3.5 MV accelerator of the Bellotti Ion Beam Facility (IBF) now available underground at LNGS, LUNA extends its reach to the higher energies and beam intensities that characterise explosive stellar environments. I will present the experimental programme including the reactions involved in explosive nucleosynthesis. The ¹²C+¹²C fusion reaction, measured through its ¹²C(¹²C,p)²³Na and ¹²C(¹²C,α)²⁰Ne channels, governs carbon ignition and thus thermonuclear (type Ia) supernovae and superbursts. In parallel, the competing ²²Ne(α,γ)²⁶Mg and ²²Ne(α,n)²⁵Mg reactions fix the branching that sets the dominant neutron source for the s process in massive stars and during explosive shell burning. Together, these LUNA measurements sharpen the nuclear input to models of stellar explosions and their associated outflows.

Constraining the 25Al(p,γ)26Si resonant reaction rate in classical novae via experimental study of the 25Mg(d,p)26Mg reaction (YRP)

• Nathan Giha (IJCLab)

Observation of the 1.809-MeV $\gamma$ ray from $^{26}$Al decay ($T_{1/2} = 7.17\times10^5$ yr) in our galaxy evinces that nucleosynthesis is currently ongoing. $^{26}$Al is produced in a variety of stellar sites, including classical novae. For the temperatures reached in classical novae, an alternative $^{26}$Al production pathway exists via the $^{25}$Al($p,\gamma$)$^{26}$Si($\beta^+$)$^{26}$Al$^\text{m}$ reaction, wherein the $^{26}$Al$^\text{m}$ decays directly to the $^{26}$Mg ground state and does not emit the characteristic $\gamma$ ray. Thus, the total amount of 1.809-MeV $\gamma$-ray emission depends strongly on the $^{25}$Al($p$,$\gamma$)$^{26}$Si reaction rate, which has been identified as the main source of uncertainty in determining the $^{26}$Al production in classical novae. To improve our knowledge of the $^{26}$Si resonances above the proton threshold that contribute to this rate, we study the analog states of the mirror nucleus $^{26}$Mg using a neutron transfer reaction, $^{25}$Mg($d,p$)$^{26}$Mg. This reaction was measured at the Split-Pole magnetic spectrometer at the ALTO facility of IJCLab, with a 12-MeV deuteron beam impinging on an enriched $^{25}$MgO target. I will present our results in the context of the nearly two orders of magnitude tension in the literature [Yas90, Ham20] for the neutron spectroscopic factor of the 5.691-MeV ($1^+$) state. The analog 5.676-MeV ($1^+$) resonance in $^{26}$Si is one of three resonances expected to dominate the reaction rate at nova burning temperatures. [Yas90] M. Yasue et al. Phys Rev C 42, 4 (1990)

Heavy Elements as Clues to the Progenitors of Type Ia Supernovae: the Case of He‑Accreting White Dwarfs

• Umberto Battino (University of Naples "Federico II")

Type Ia supernovae (SNIa) are fundamental probes of cosmic expansion and major contributors to Galactic chemical evolution, yet the nature of their progenitors remains unsettled. Two main progenitor classes can be identified: the explosion of a near-Chandrasekhar-mass or a sub-Chandrasekhar-mass white dwarf. In recent work (Battino et al. 2025), complemented by earlier studies (Battino et al. 2020), we performed the first full nucleosynthesis calculations during the formation of near-Chandrasekhar white dwarfs in two key scenarios: slow merger of CO white dwarfs and H-accretion from a non-degenerate companion. We demonstrated that, in both cases, pre-explosive nuclear burning in the outer layers activates the $^{22}$Ne($\alpha$,n)$^{25}$Mg neutron source, efficiently producing trans-Fe elements like Rb, Sr, and Kr (exceeding their initial abundance by 1000 times), which will be ejected by the following explosion. In this contribution, I present new theoretical results covering the last remaining channel able to form a near-Chandrasekhar SNIa progenitor: rapidly He-accreting white dwarfs ($\dot{M} \sim 10^{-6}\,M_{\odot}\,\mathrm{yr}^{-1}$). Also in this case, the $^{22}$Ne($\alpha$,n)$^{25}$Mg neutron source is activated during recurrent He-flashes along the accretion process, producing a thick surface layer highly enriched in trans-Fe species. Additionally, we discuss the case of slowly He-accreting white dwarfs ($10^{-8} < \dot{M}/(M_{\odot}\,\mathrm{yr}^{-1}) < 10^{-7}$), which are likely to end in a sub-Chandrasekhar explosion. While our preliminary results show that some trans-Fe production could also take place in this case, the heavy-element-enriched layer is very thin. This would severely limit the trans-Fe ejected yields from sub-Chandrasekhar explosions, likely to values at least 100 times lower than the yields from near-Chandrasekhar explosions. We therefore confirm that a significant production of trans-Fe elements in SNIa progenitors can only be hosted by near-Chandrasekhar systems. This provides strong support for the use of trans-Fe species as a previously unexplored spectroscopic signature to discriminate between near- and sub-Chandrasekhar explosions.

Concluding remarks and poster prize

NuFFER: NuPECC Forum For Early-career Researchers

• Eliana Masha

The NuPECC Forum For Early-career Researchers (NuFFER) is a platform dedicated to support early-career researchers (ECRs) in nuclear physics across Europe. Established under NuPECC’s guidance, NuFFER aims to build up a strong, connected, and visible community of ECRs, ensuring that their voices are represented in discussions influencing the future of nuclear physics research. The forum supports ECRs’ professional and personal development by promoting networking opportunities with senior researchers, advocating for career advancement, and organizing workshops on key topics. The NuFFER steering committee, composed of representatives from all NuPECC member countries, ensures that diverse perspectives are heard. NuFFER will strengthen ECR engagement in scientific and policy dialogues, through regular meetings and annual events, contributing to a more inclusive and dynamic nuclear physics community. The NuFFER initiative will be presented and the feedback from both young researchers and experienced professionals will be greatly considered in advancing the development of this community, ensuring its success and relevance in the field.