Tue·Dec 9, 2025Tuesday·December 9, 2025

1. 01*

   Enhanced nuclear fusion in the sub-keV energy regime

   Micah. E. Karahadian · Matthew Colborne · Arun Persaud · Thomas Schenkel🇺🇸 · Jeremy N. Munday

   Nuclear fusion requires overcoming or traversing a repulsive Coulomb barrier of hundreds of kiloelectronvolts, rendering the probability of fusion at sub-keV energies vanishingly small. Yet in condensed matter, the electronic and structural environment of reacting nuclei can profoundly alter fusion rates. Here we demonstrate that deuterium-deuterium fusion within metallic foils exhibits a pronounced enhancement and reaction yield plateau below energies of 2.5 keV- contrary to the expected exponential suppression with decreasing energy. Using a dual-chamber platform that combines electrochemical deuterium loading with ion-beam bombardment, we show that fusion yields in palladium and titanium hydrides are enhanced by over 10^18 compared to theoretical bare-nucleus fusion rates. These results demonstrate that access to low-energy fusion processes can be governed by materials degrees of freedom. This materials-driven fusion regime establishes a reproducible, tunable framework for studying and ultimately engineering nuclear reactions in solids. While the reaction rates reported here are low, these insights into materials-modulated fusion processes offer a potential foundation for understanding how condensed-matter environments could influence future fusion-energy concepts.

   nucl-excond-mat.mtrl-sciNature Commun.(2026)·1 citation
2. 02*

   Identified charged hadron production in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 54.4 GeV with the STAR detector

   STAR Collaboration: B. E. Aboona🇺🇸 · J. Adam🇨🇿 · G. Agakishiev🇷🇺 · I. Aggarwal🇮🇳 · M. M. Aggarwal🇮🇳 · Z. Ahammed🇮🇳 · A. Aitbayev🇷🇺 · I. Alekseev🇷🇺 · E. Alpatov🇷🇺 · A. K. Alshammri🇺🇸 · A. Aparin🇷🇺 · S. Aslam🇮🇳 and 375 other authors

   We present results on the production of ${\pi }^{\pm }$, $K^{\pm }$, $p$, and $\bar{p}$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 54.4~GeV using the STAR detector at RHIC, at midrapidity ($|y|<$ 0.1). Invariant yields of these particles as a function of transverse momentum are shown. We determine bulk properties such as integrated particle yields ($dN/dy$), mean transverse momentum ($⟨p_T⟩$), particle ratios, which provide insight into the particle production mechanisms. Additionally, the kinetic freezeout parameters ($T_{\text{kin}}$ and $⟨{\beta }_T⟩$), which provide information about the dynamics of the system at the time of freezeout, are obtained. The Bjorken energy density (${ϵ}_{\mathrm{BJ}}$), which gives an estimate of the energy density in the central rapidity region of the collision zone at the formation time $\tau$, is calculated and presented as a function of multiplicity for various energies. The results are compared with those from the models such as A Multi-Phase Transport (AMPT) and Heavy Ion Jet INteraction Generator (HIJING) for further insights.

   nucl-exhep-exhep-phhep-th+1PRC(2026)·2 citations
3. 03*

   New results on $\varphi$(1020) production from the NA61/SHINE experiment at CERN SPS

   Antoni Marcinek🇵🇱

   NA61/SHINE is a multipurpose, fixed-target hadron spectrometer at the CERN SPS. Its research program includes studies of strong interactions as well as reference measurements for neutrino and cosmic-ray physics. A significant advantage of NA61/SHINE over collider experiments is its extended coverage of phase space available for particle production. This includes the entire projectile hemisphere of the collision, with no low-pT cut-off. The energy and system-size dependence of strangeness production plays an essential role in studies of the transition from confined to deconfined matter. With its zero net strangeness and its valence structure composed predominantly of s and $\bar{s}$ valence quarks, the $\varphi$(1020) meson will not be sensitive to strangeness-related effects in a purely hadronic scenario, but will behave like a doubly strange particle in a partonic system. This contribution presents the first-ever results on $\varphi$(1020) meson production in intermediate-size systems at the CERN SPS, that is, central Ar+Sc collisions at $\sqrt{s_{\text{NN}}}$ = 8.8, 11.9, and 16.8 GeV. The presented results include double-differential rapidity-transverse momentum (y-pT) distributions, transverse mass (mT) spectra at midrapidity, pT-integrated rapidity spectra, mean multiplicities (4$\pi$ yields), and particle ratios. These are compared to data on Pb+Pb and p+p collisions. A discussion of open and hidden strangeness production enhancement is included. Finally, a comparison with three microscopic models is shown, demonstrating their overall failure in describing these new measurements.

   nucl-exhep-exUkr.J.Phys.(2026)·1 citation
4. 04*

   Detailed study of non-equilibrium characteristics of quasi-neutral TNSA plasmas

   Zhe Zhu🇨🇳 · A. Bonasera🇺🇸 · D. Batani🇫🇷 · M. R. D. Rodrigues🇫🇷 · K. Batani🇵🇱 · J.A. Pérez-Hernández🇪🇸 · M. Ehret🇪🇸 · E. Filippov · H. Larreur🇪🇸 · D. Molloy🇬🇧 · G. G. Rapisarda🇮🇹 · D. Lattuada🇮🇹 and 17 other authors

   In an experiment performed in November 2022 at the petawatt (PW) laser facility at Vega III located in Salamanca-Spain, we have studied the successful production of several radioisotopes using protons accelerated by the Target Normal Sheath Acceleration (TNSA) mechanism (Rodrigues et al. [1]). The experimental proton energy distribution recorded on a shot-to-shot basis and confirmed in a follow up experiment (K. Batani et al. [2]), allowed us to derive the number of nuclear reactions taking place in different targets on a single shot. From this analysis, using the ratio of the yields 11C/7Be, we obtained an effective "single shot" temperature of the TNSA plasma. We used this value to evaluate the yield of alpha particles from the reaction p + 11B -> 3 alpha which may reach (1.6 +/- 0.5) x 10^9 alpha particles in 2pi. From the fluctuations of the protons and the fusion yields, we derived a "TNSA-Equation of State" (EoS), The deviation of such "EoS" from the classical ideal gas limit is well reproduced by the soliton solution of the Korteweg-de Vries (KdV) equation for each shot.

   ↳ physics.plasm-phnlin.PSnucl-ex0 citations
5. 05*

   Observation of two nuclear recoil peaks induced by neutron capture on Al2O3

   H. Abele🇦🇹 · P. Ajello🇩🇪 · B. Arnold🇦🇹 · E. Bossio🇫🇷 · J. Burkhart🇦🇹 · F. Cappella🇮🇹 · N. Casali🇮🇹 · R. Cerulli🇮🇹 · J-P. Crocombette🇫🇷 · G. del Castello🇮🇹 · M. del Gallo Roccagiovine🇮🇹 · P. de Marcillac🇫🇷 and 34 other authors

   We report the observation of two nuclear recoil peaks induced by neutron capture on aluminum in a cryogenic Al${}_2$O${}_3$ detector developed by the NUCLEUS collaboration for the detection of reactor neutrinos via coherent elastic neutrino-nucleus (CEvNS) process. Data collected at the Technical University of Munich in 2024 with a ${}^{252}$Cf source reveal a main recoil line at 1145 eV from single-$\gamma$ de-excitation of ${}^{28}$Al and a newly observed structure near 575 eV originating from several two-$\gamma$ cascades. The latter constitutes the first direct measurement of a nuclear recoil line induced by multi-$\gamma$ cascades. It is predicted by our simulations when the recoiling nucleus has time to stop before the emission of the next $\gamma$-ray in the cascade. These results demonstrate the potential performance of the CRAB (Calibration Recoil for Accurate Bolometry) method for in situ nuclear recoil calibration and highlight the importance of accurately modeling recoil stopping and nuclear de-excitation times in cryogenic detectors of CEvNS and dark matter interactions.

   ↳ physics.ins-detnucl-exPRC(2026)·0 citations
6. 06*

   Understanding Charge Radii with Machine Learning: Discovering Physics Expressions

   B. Maheshwari🇫🇷 · P. Van Isacker🇫🇷

   We introduce a robust, interpretable machine learning (ML) framework that combines numerical regression for high-accuracy predictions with symbolic regression to uncover the underlying physics. This hybrid approach effciently derives analytical expressions by leveraging the smoothed predictions of optimized ML models, a significant acceleration over direct symbolic regression on raw experimental data. We apply this framework, as an example, to nuclear charge radii across the nuclear chart, notably including light nuclei that are often excluded from such studies. We employ Light Gradient Boosting Machine (LGBM) and Gaussian Process Regression (GPR) models to map correlations between charge radii and key physical features: mass $A^{1/3}$ and proton number $Z^{1/3}$ dependencies, total binding energy, and for the first time, the pairing gap. Our models are rigorously trained using four-fold cross-validation with automated hyperparameter optimization, ensuring robustness and generalizability, which is critical for the typically small and skewed datasets in nuclear physics. Finally, we distill the knowledge from the initial LGBM and GPR models into simplified, interpretable mathematical expressions via symbolic regression, white-boxing these ML models. The derived formulas provide physical insights comparable to traditional many-body models and demonstrate a powerful pathway for physics expression discovery guided by ML.

   ↳ nucl-thnucl-exPLB(2026)·2 citations
7. 07*

   Lineshape response of plastic scintillator to pair production of 4.44 MeV gamma's

   Melisa Ozen · John A. Behr🇨🇦 · Michelle Khoo · Felix Klose · Alexandre Gorelov🇨🇦 · Dan Melconian🇺🇸

   We measure the distribution of energy deposited in a 40x88 mm plastic scintillator by e+ e- pair production of 4.44 MeV gamma-rays. We observe the double-escape peak of 3.42 MeV from pair production by tagging 511 keV annihilation radiation in two high-Z scintillators. The source is a standard commercial neutron source using alpha-emitting 241Am encapsulated with 9Be, which has a reaction branch feeding the first Ipi=2+ state of 12C making the 4.44 MeV gamma-rays. We demonstrate the extraction of the double-escape peak from the large neutron-produced backgound, and explore some of the features and difficulties of this technique with our apparatus.

   ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2023)·2 citations
8. 08*

   Bound and Resonant States of Muonic Few-Body Coulomb Systems: Extended Stochastic Variational Approach

   Liang-Zhen Wen🇨🇳 · Shi-Lin Zhu🇨🇳

   We compute the bound and resonant states of hydrogen-like muonic ions ($\mu \mu p$, $\mu \mu d$, $\mu \mu t$) and three-body muonic molecular ions ($pp\mu$, $pd\mu$, $pt\mu$, $dd\mu$, $dt\mu$, $tt\mu$), and the four-body double-muonic hydrogen molecule ($\mu \mu pp$) using an extended stochastic variational method combined with complex scaling. The approach provides a unified treatment of bound and quasibound states and achieves an energy accuracy better than $0.1\mathrm{eV}$ across all systems studied. Complete spectra below the corresponding $n=2$ atomic thresholds are obtained, including several previously unresolved shallow resonances in both three- and four-body sectors.

   ↳ physics.atom-phhep-exhep-phnucl-exPRA(2026)·3 citations
9. 09*

   Theory of inverse beta decay for reactor antineutrinos

   Oleksandr Tomalak🇨🇳 · Qishan Liu🇨🇳 · Yu-Feng Li🇨🇳

   Inverse beta decay (IBD), ${\overline{\nu }}_{e}p\to e^{+}n\left(\gamma \right)$, is the main detection channel for reactor antineutrinos in water- and hydrocarbon-based detectors. As reactor antineutrino experiments now target sub-percent-level sensitivity to oscillation parameters, a precise theoretical description of IBD, including recoil, weak magnetism, nucleon structure, and radiative corrections, becomes essential. In this work, we give a detailed and precise calculation of the total and differential cross sections for radiative IBD, ${\overline{\nu }}_{e}p\to e^{+}n\gamma$. We use a heavy baryon chiral perturbation theory framework, systematically incorporating electroweak, electromagnetic, and strong-interaction corrections. We derive new analytic cross-section expressions, clarify the collinear structure of radiative corrections, and provide a systematic uncertainty analysis. We also discuss phenomenological applications for reactor antineutrino experiments, e.g., JUNO, and neutron decay. Our results enable sub-permille theoretical precision, supporting current and future experiments.

   ↳ hep-phhep-exnucl-exnucl-thPhys. Rev. D (2026)·8 citations
10. 10*

    Radiative corrections to inverse beta decay: a precision analysis for reactor neutrinos

    Oleksandr Tomalak🇨🇳

    We present a complete calculation of radiative corrections to the inverse beta decay reaction, ${\overline{\nu }}_e+p\to e^{+}+n$, at reactor antineutrino energies using heavy-baryon chiral perturbation theory. Our analysis consistently incorporates quantum electrodynamics, chromodynamics, and electroweak contributions for the first time within this framework. We provide updated, high-precision cross-section predictions with a full error budget and present the positron energy spectrum, including radiative effects. The results are essential for normalizing the reactor antineutrino flux, determining neutrino oscillation parameters with subpercent accuracy, and searching for new physics at nuclear power plants.

    ↳ hep-phhep-exnucl-exnucl-thPhys. Rev. Lett. (2026)·5 citations

* 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.