Fri·Dec 5, 2025Friday·December 5, 2025

1. 01*

   The ${}^{18}$O$(p,n{)}^{18}$F Reaction as a Quasi-stellar Neutron Source

   Sarah Agus-Bina

   The s-process in AGB stars produces elements with atomic mass numbers $A\gtrsim 60$ through successive neutron captures and beta decays. In stellar environments where the s-process occurs, neutrons quickly thermalize, adopting a Maxwell-Boltzmann energy distribution determined by the local temperature independent of their production via ($\alpha$,n) reactions. Laboratory experiments reproduce this Maxwell-Boltzmann neutron energy spectrum using (p, n) reactions. Specifically, the 7Li(p,n)7Be reaction is commonly employed to measure s-process cross-sections at kT$\approx$25 keV. Expanding the range of reactions used for measuring neutron-induced s-process cross-sections can offer valuable insights into the s-process in AGB stars. One such reaction is 18O(p,n)18F, which can be used to mimic s-process cross-sections, as its neutron energy distribution is similar to the thermal flux distribution at the stellar environment where the 13C($\alpha$,n)16O reaction (kT = 8 keV) takes place. Heil et al. showed that the neutron energy spectrum emitted from the 18O(p,n)18F reaction at proton energy of Ep = 2582 keV, close to the reaction threshold of 2574 keV, closely resembles a Maxwellian flux with kT$\approx$5 keV. This experiment was repeated at PTB and a computational tool, OxyGen, was created to calculate the expected neutron energy spectrum and angular distribution at a planned liquid water-based 18O target at SARAF. OxyGen was incorporated into Geant4 transport simulations, which were compared to experimental results. Overall, the findings of this thesis demonstrate that the OxyGen simulation provides a reliable prediction of the neutron energy spectrum for the 18O(p,n)18F reaction and can be effectively used to plan and analyze future experiments at SARAF for different proton energies.

   nucl-ex0 citations
2. 02*

   Precise ${}^{136}$Xe Double Beta Decay Measurement in PandaX-4T with Implications on the Nuclear Matrix Elements and Majorons

   PandaX Collaboration: Zhe Yuan🇨🇳 · Zihao Bo🇨🇳 · Wei Chen🇨🇳 · Xun Chen🇨🇳 · Yunhua Chen🇨🇳 · Chen Cheng🇨🇳 · Xiangyi Cui🇨🇳 · Manna Deng🇨🇳 · Yingjie Fan🇨🇳 · Deqing Fang🇨🇳 · Xuanye Fu🇨🇳 · Zhixing Gao🇨🇳 and 101 other authors

   The continuous spectrum of double beta decay ($\beta \beta$) provides a sensitive probe to test the predictions of the standard model and to search for signatures of new physics beyond it. We present a comprehensive analysis of the ${}^{136}$Xe $\beta \beta$ spectrum utilizing $39.1\pm 0.7\text{kg}\cdot \text{yr}$ of ${}^{136}$Xe exposure from the PandaX-4T experiment. The analysis yields the most precise measurement to date of the ${}^{136}$Xe two-neutrino double beta decay ($2\nu \beta \beta$) half-life, $(2.14\pm 0.05)\times 10^{21}$ years, the uncertainty of which is reduced by a factor of 2 compared to our previous result. We measure the parameter ${\xi }_{31}^{2\nu }$, defined as the ratio between the subleading and leading components of the ${}^{136}$Xe $2\nu \beta \beta$ nuclear matrix element, to be $0.59_{-0.38}^{+0.41}$, which is consistent with theoretical predictions. We also search for Majoron-emitting modes of ${}^{136}$Xe $\beta \beta$, establishing the most stringent limit for the spectral index $n=7$.

   nucl-exhep-exPRL(2026)·6 citations
3. 03*

   First Study of the Nuclear Response to Fast Hadrons via Angular Correlations between Pions and Slow Protons in Electron-Nucleus Scattering

   S.J. Paul🇺🇸 · M. Arratia🇺🇸 · H. Hakobyan🇨🇱 · W. Brooks🇨🇱 · A. Acar🇬🇧 · P. Achenbach🇺🇸 · J.S. Alvarado🇫🇷 · W.R. Armstrong🇺🇸 · N.A. Baltzell🇺🇸 · L. Barion🇮🇹 · M. Bashkanov🇬🇧 · M. Battaglieri🇮🇹 and 118 other authors

   We report on the first measurement of angular correlations between high-energy pions and slow protons in electron-nucleus ($eA$) scattering, providing a new probe of how a nucleus responds to a fast-moving quark. The experiment employed the CLAS detector with a 5-GeV electron beam incident on deuterium, carbon, iron, and lead targets. For heavier nuclei, the pion-proton correlation function is more spread-out in azimuth than for lighter ones, and this effect is more pronounced in the $\pi p$ channel than in earlier $\pi \pi$ studies. The proton-to-pion yield ratio likewise rises with nuclear mass, although the increase appears to saturate for the heaviest targets. These trends are qualitatively reproduced by state-of-the-art $eA$ event generators, including BeAGLE, eHIJING, and GiBUU, indicating that current descriptions of target fragmentation rest on sound theoretical footing. At the same time, the precision of our data exposes model-dependent discrepancies, delineating a clear path for future improvements in the treatment of cold-nuclear matter effects in $eA$ scattering.

   nucl-exPLB(2026)·0 citations
4. 04*

   Nucleon Short-Range Correlations and High-Momentum Dynamics: Implications on the Equation of State of Dense Matter

   Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸 · Yu-Gang Ma🇨🇳

   Nucleon short-range correlations (SRCs) and their high-momentum tails (HMTs) encode key short-range dynamics in nuclei and dense matter. This review provides a concise overview of SRC features relevant to the Equation of State (EOS) of isospin-asymmetric nuclear matter. We summarize empirical and theoretical properties of the single-nucleon momentum distribution $n(k)$, emphasizing the role of the neutron--proton tensor force, the dominance of correlated np pairs, and the enhancement of minority-species HMTs. Links to nucleon effective E-masses, quasi-deuteron components, and orbital entanglement are briefly noted. We examine how SRC-induced HMTs modify kinetic and potential contributions to the EOS in both non-relativistic and relativistic frameworks, including the softening of the kinetic symmetry energy and departures from the isospin parabolic approximation of asymmetric nuclear EOS. Sensitivity to high-momentum components and generalizations to arbitrary dimensions are also highlighted. Implications for heavy-ion reactions are summarized, including effects on particle yields, collective flows, deeply sub-threshold particle production and hard photon emission, driven by modified initial nucleon momentum distributions and abundant high relative-momentum np pairs during the reaction. Finally, we outline SRC-HMT consequences for neutron-star matter, covering proton fractions, tidal deformabilities, $Z$-factors, cooling, and the core--crust transition, as well as possible connections to dark-matter interactions in dense environments.

   ↳ nucl-thastro-ph.HEhep-thnucl-exEuro Phys J. Special Topic (2026): Explor…·10 citations
5. 05*

   Exploring the QCD phase diagram through correlations and fluctuations

   Volker Koch🇺🇸 · Volodymyr Vovchenko🇺🇸

   The exploration of the Quantum Chromodynamics (QCD) phase diagram is a central goal of relativistic heavy-ion collision experiments. This review focuses on the role of fluctuations and correlations as sensitive probes of the phase structure. We discuss theoretical advancements and experimental methodologies employed to map the QCD phase diagram, highlighting constraints derived from both lattice QCD calculations and existing experimental data. Key observables such as cumulants and factorial cumulants of conserved charges (e.g., net-proton, net-charge) are explored as promising signatures of phase transitions and the QCD critical point. We discuss how these quantities are measured experimentally and compared with theoretical predictions, addressing challenges and best practices for meaningful comparisons. Special attention is given to predictions and current experimental results at high baryon density, including recent findings from the STAR collaboration at RHIC. Finally, we identify open issues and future directions for fluctuation and correlation studies at lower collision energies, relevant for future measurements, for example by the CBM experiment.

   ↳ nucl-thhep-phnucl-exEur.Phys.J.ST(2026)·10 citations
6. 06*

   Nucleon to Roper transition amplitudes and electromagnetic form factors

   G. Ramalho🇰🇷

   The second excitation of the nucleon, the Roper, has properties differentiated from other low-lying nucleon resonances. Their properties challenge our understanding of the structure of the baryons in terms of the degrees of freedom from QCD. In the present work we discuss the properties of the Roper resonance and the nucleon to Roper electromagnetic transition, based on the quark degrees of freedom, that are expected to dominate for large square momentum transfer $Q^2$. We also discuss the analytic structure of the transition amplitudes in the low-$Q^2$ region, and how the contributions of baryon-meson states can help to describe the low and intermediate $Q^2$ data, and the nature of the Roper.

   ↳ hep-phhep-exhep-latnucl-ex+1Acta Phys.Polon.B(2026)·2 citations
7. 07*

   Complex-energy eigenvector continuation for nuclear many-body broad resonances

   Rongzhe Hu🇨🇳 · Nicolas Michel · Zhicheng Xu🇨🇳 · Jianguo Li🇨🇳 · Furong Xu🇨🇳

   Broad resonances are a unique phenomenon in nuclear many-body systems. Theoretical studies usually involve the continuum degree of freedom, which drastically increases the model space of calculations, and may lead to non-convergence or instability of computations. In this paper, we present the extension of the eigenvector continuation (EC) method to the complex-energy space to treat the broad resonances of open quantum systems of nuclei. EC provides an efficient method to predict the solution of a large-space many-body problem within a small subspace. Using only a few bound and narrow resonance solutions as input in EC, we can obtain the solution of a broad resonance. We have applied the complex-energy EC to the broad resonances of ${}^4$H, four-neutron ${}^{4}n$, ${}^6$He and ${}^7$He systems.

   ↳ nucl-thnucl-exPLB(2026)·3 citations
8. 08*

   Experimental study of the reaction ${\Xi }^{0}n\to \Lambda \Lambda X$ using ${\Xi }^0$-nucleus scattering

   BESIII Collaboration: M. Ablikim · M. N. Achasov · P. Adlarson · X. C. Ai · R. Aliberti · A. Amoroso · Q. An · Y. Bai · O. Bakina · Y. Ban · H.-R. Bao · V. Batozskaya and 719 other authors

   Using $(10087\pm 44)\times 10^6$$J/\psi$ events collected with the BESIII detector operating at the BEPCII storage ring in $2009$, $2012$, $2018$, and $2019$, we perform a search for the reaction ${\Xi }^{0}n\to \Lambda \Lambda X$, where $X$ denotes any additional final particles. Given the highly suppressed phase space for producing extra pions, the $X$ consists of either nothing or a photon, corresponding to the processes ${\Xi }^{0}n\to \Lambda \Lambda$ and ${\Xi }^{0}n\to \Lambda {\Sigma }^0\to \Lambda \Lambda \gamma$. The ${\Xi }^0$ comes from the decay of $J/\psi \to {\Xi }^0{\bar{\Xi }}^0$, while the neutron originates from material of the beam pipe. A signal is observed for the first time with a statistical significance of 6.4$\sigma$. The cross section for the reaction ${\Xi }^0+{}^9\mathrm{Be}\to \Lambda +\Lambda +X$ is measured to be $(43.6\pm 10.5_{\text{stat}}\pm 11.1_{\text{syst}})$ mb at $P_{{\Xi }^0}\approx 0.818$ GeV/$c$, where the first uncertainty is statistical and the second systematic. No significant $H$-dibaryon signal is observed in the $\Lambda \Lambda$ final state.

   ↳ hep-exnucl-exPRC(2026)·2 citations
9. 09*

   The program Simourg for simulating the response functions of gamma detectors with simple geometries

   V.V.Kobychev🇺🇦

   The program Simourg (Simulator of Usually Requested Geometries) is based on the Geant4 toolkit and created for Monte Carlo simulation of gamma-ray spectrometric nuclear detectors with a simple axial symmetric geometry, which is typical for many tasks of studying the decay of long-lived nuclei and measuring the radioactivity of natural objects. The program is designed for quick estimation of the effectiveness and the response function of the detector to monoenergetic gamma quanta in the energy range from keV to several MeV.

   ↳ physics.ins-detnucl-exNucl. Physics and Atomic Energy. 2011, Vo…·1 citation

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.