Tue·Jan 7, 2025Tuesday·January 7, 2025

1. 01*

   Direct observation of $\beta$ and $\gamma$ decay from a high-spin long-lived isomer in ${}^{187}$Ta

   J. L. Chen🇨🇳 · H. Watanabe🇯🇵 · P. M. Walker🇬🇧 · Y. Hirayama · Y. X. Watanabe🇺🇸 · M. Mukai · C. F. Jiao🇨🇳 · M. Ahmed🇩🇪 · M. Brunet · T. Hashimoto · S. Ishizawa · F. G. Kondev and 11 other authors

   ${}^{187}$Ta ($Z=73$, $N=114$) is located in the neutron-rich $A\approx 190$ region where a prolate-to-oblate shape transition via triaxial softness is predicted to take place. A preceding work on the $K^{\pi }=(25/2^{-})$ isomer and a rotational band to which the isomer decays carried out by the same collaboration revealed that axial symmetry is slightly violated in this nucleus. This paper focuses on a higher-lying isomer, which was previously identified at 2933(14) keV by mass measurements with the Experimental Storage Ring at GSI. The isomer of interest has been populated by a multi-nucleon transfer reaction with a ${}^{136}$Xe primary beam incident on a natural tungsten target, using the KEK Isotope Separation System at RIKEN. New experimental findings obtained in the present paper include the internal and external $\beta$-decay branches from the high-spin isomer and a revised half-life of 136(24) s. The evaluated hindrances for $K$-forbidden transitions put constraints on the spin-parity assignment, which can be interpreted as being ascribed to a prolate shape with a five-quasiparticle configuration by model calculations.

   nucl-exnucl-thPRC(2025)·2 citations
2. 02*

   First Measurement of $a_2^0(1320)$ Polarized Photoproduction Cross Section

   GlueX Collaboration: F. Afzal🇩🇪 · C. S. Akondi🇺🇸 · M. Albrecht🇺🇸 · M. Amaryan🇺🇸 · S. Arrigo🇺🇸 · V. Arroyave🇺🇸 · A. Asaturyan🇺🇸 · A. Austregesilo🇺🇸 · Z. Baldwin🇺🇸 · F. Barbosa🇺🇸 · J. Barlow🇺🇸 · E. Barriga🇺🇸 and 139 other authors

   We measure for the first time the differential photoproduction cross section $d\sigma /dt$ of the $a_2(1320)$ meson at an average photon beam energy of 8.5~GeV, using data with an integrated luminosity of 104~pb${}^{-1}$ collected by the GlueX experiment. We fully reconstruct the $\gamma p\to \eta {\pi }^{0}p$ reaction and perform a partial-wave analysis in the $a_2(1320)$ mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. These measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states.

   nucl-exhep-exPRC(2025)·5 citations
3. 03*

   The MAJORANA DEMONSTRATOR experiment's construction, commissioning, and performance

   N. Abgrall🇨🇭 · E. Aguayo · I.J. Arnquist🇺🇸 · F.T. Avignone III🇺🇸 · A.S. Barabash🇷🇺 · C.J. Barton🇺🇸 · P.J. Barton🇺🇸 · F.E. Bertrand · E. Blalock🇺🇸 · B. Bos🇺🇸 · M. Boswell · A.W. Bradley and 99 other authors

   Background: The MAJORANA DEMONSTRATOR , a modular array of isotopically enriched high-purity germanium (HPGe) detectors, was constructed to demonstrate backgrounds low enough to justify building a tonne-scale experiment to search for the neutrinoless double-beta decay ($\beta \beta (0\nu )$) of ${}^{76}\mathrm{Ge}$. Purpose: This paper presents a description of the instrument, its commissioning, and operations. It covers the electroforming, underground infrastructure, enrichment, detector fabrication, low-background and construction techniques, electronics, data acquisition, databases, and data processing of the MAJORANA DEMONSTRATOR. Method: The MAJORANA DEMONSTRATOR operated inside an ultra-low radioactivity passive shield at the 4850-foot~level of the Sanford Underground Research Facility (SURF) from 2015-2021. Results and Conclusions: The MAJORANA DEMONSTRATOR achieved the best energy resolution and second-best background level of any $\beta \beta (0\nu )$ search. This enabled it to achieve an ultimate half-life limit on $\beta \beta (0\nu )$ in ${}^{76}\mathrm{Ge}$ of $8.3\times 10^{25}$~yr (90\% C.L.) and perform a rich set of searches for other physics beyond the Standard Model.

   ↳ physics.ins-detnucl-ex8 citations
4. 04*

   Proton Radiation Damage and Annealing of COSI p-type Cross-strip HPGe Detectors

   Sophia E. Haight · Steven E. Boggs · Gabriel Brewster · Sean N. Pike · Jarred M. Roberts · Albert Y. Shih · Joanna M. Szornel🇺🇸 · John A. Tomsick🇺🇸 · Aravind B. Valluvan · Andreas Zoglauer

   In order to understand the effects of a space radiation environment on cross-strip germanium detectors, we investigated the effects of high-energy proton damage on a COSI detector and the capabilities of high-temperature annealing in repairing detector spectral resolution. We irradiated a COSI-balloon cross-strip high-purity germanium (HPGe) detector with 150 MeV protons resulting in a net fluence of $4.95\times 10^8$ p${}^{+}$/cm${}^2$ and corresponding to ~10 years in COSI's space radiation environment. We repaired the resulting degradation in spectral resolution through a series of high-temperature anneals to obtain a final FWHM of 4.08 keV, within 37% of its preradiation value (2.98 keV FWHM). We characterized the repair of charge traps with time spent under high-temperature anneal to inform an annealing procedure for long-term maintenance of COSI's spectral resolution.

   ↳ physics.ins-detastro-ph.IMnucl-exNucl.Instrum.Meth.A(2025)·0 citations
5. 05*

   Evolutions of in-medium baryon-baryon scattering cross sections and stiffness of dense nuclear matter from Bayesian analyses of FOPI proton flow excitation functions

   Bao-An Li🇺🇸 · Wen-Jie Xie🇨🇳

   Within a Bayesian statistical framework using a Gaussian Process (GP) emulator for an isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model simulator of heavy-ion reactions with momentum-independent Skyrme interactions, we infer from the proton directed and elliptical flow in mid-central Au+Au reactions at beam energies from 150 to 1200 MeV/nucleon taken by the FOPI Collaboration the posterior Probability Distribution Functions (PDFs) of the in-medium baryon-baryon scattering cross section (BBSCS) modification factor $X$ (with respect to their free-space values) and the stiffness parameter $K$ of dense nuclear matter. We find that the most probable value of $X$ evolves from around 0.7 to 1.0 as the beam energy $E_{beam}/A$ increases. On the other hand, the posterior PDF($K$) may have dual peaks having roughly the same height or extended shoulders at high $K$ values. More quantitatively, the posterior PDF($K$) changes from having a major peak around 220 MeV characterizing a soft EOS in the reaction at $E_{beam}/A$=150 MeV to one that peaks around 320 MeV indicating a stiff EOS in the reactions at $E_{beam}/A$ higher than about 600 MeV. The transition from soft to stiff happens in mid-central Au+Au reactions at beam energies around 250 MeV/nucleon in which $K=220$ MeV and $K=320$ MeV are approximately equally probable. Altogether, the FOPI proton flow excitation function data indicate a gradual hardening of hot and dense nuclear matter as its density and temperature increase in reactions with higher beam energies.

   ↳ nucl-thastro-ph.HEnucl-exPRC(2025)·11 citations
6. 06*

   Extracting the Speed of Sound in Heavy-Ion Collisions: A Study of Quantum-Initiated Fluctuations and Thermalization

   Yu-Shan Mu🇨🇳 · Jing-An Sun🇨🇳 · Li Yan🇨🇳 · Xu-Guang Huang🇨🇳

   The thermalization of quark-gluon plasma created in heavy-ion collisions is crucial for understanding its behavior as a relativistic fluid and the thermodynamic properties of the Quantum Chromodynamics (QCD). This study investigates the role of fluctuations in the relationship between transverse momentum and particle multiplicity, with a particular focus on their impact on extracting the QCD speed of sound. In a thermalized quark-gluon plasma, these fluctuations mostly originate from quantum fluctuations in the colliding nuclei, and exhibit a Gaussian distribution as a consequence of their independence from thermodynamic response. In contrast, non-thermalized systems display non-Gaussian fluctuations, reflecting the breakdown of thermalization. By leveraging the Gaussianity condition of quantum-initiated fluctuations, the physical value of the speed of sound can be extracted statistically, even in the presence of significant event-by-event fluctuations. This framework provides a robust diagnostic tool for probing thermalization and extracting thermodynamic properties in both large and small collision systems.

   ↳ nucl-thhep-phnucl-exPRL(2025)·13 citations
7. 07*

   Constraining the chiral magnetic effect using spectator and participant planes across Au+Au and isobar collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV

   Bang-Xiang Chen🇨🇳 · Xin-Li Zhao🇨🇳 · Guo-Liang Ma🇨🇳

   We investigate the chiral magnetic effect (CME) in relativistic heavy-ion collisions through an improved two-plane method analysis of the $\Delta \gamma$ observable, probing $\mathcal{C}\mathcal{P}$-symmetry breaking in strong interactions and topological properties of the QCD vacuum. Using a multiphase transport model with tunable CME strengths, we systematically compare Au+Au and isobar collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. We observe a reduced difference in the CME signal-to-background ratio between the spectator and participant planes for Au+Au collisions compared to isobar collisions. A comprehensive chi-square analysis across all three collision systems reveals stronger CME signatures in Au+Au collisions relative to isobar collisions, particularly when measured with respect to the spectator plane. Our findings demonstrate an enhanced experimental reliability of the two-plane method for the CME detection in Au+Au collisions.

   ↳ nucl-thhep-phnucl-exNucl.Sci.Tech.(2025)·1 citation
8. 08*

   Valence quark-stopping and gluon junction-stopping scenarios in electron-nucleus collisions at the forthcoming Electron-Ion Collider: Which one is correct?

   Ting-Ting Duan🇨🇳 · Fu-Hu Liu🇨🇳 · Khusniddin K. Olimov🇺🇿

   In the current literature, two stopping scenarios are being discussed in the context of high-energy collisions: the valence quark scenario and the gluon or baryon junction scenario. In the valence quark-stopping scenario, three valence quarks each contribute one-third of the baryon number within a baryon. Conversely, in the gluon junction-stopping scenario, the gluon junction is responsible for carrying the entire baryon number. At present, there is no consensus regarding which type of stopping scenario is correct. Based on a multi-source thermal model, our investigation indicates that the experimental data analyzed in both previous and present studies suggest that the valence quark-stopping scenario is more suitable for semi-quantitative discussions in high-energy collisions. It is anticipated that this scenario can be further validated through electron-nucleus ($eA$) collisions at the forthcoming Electron-Ion Collider (EIC).

   ↳ hep-phhep-exnucl-exnucl-th0 citations
9. 09*

   Lattice Effective Field Theory Simulations of Nuclei

   Dean Lee🇺🇸

   Lattice effective field theory applies the principles of effective field theory in a lattice framework where space and time are discretized. Nucleons are placed on the lattice sites, and the interactions are tuned to replicate the observed features of the nuclear force. Monte Carlo simulations are then employed to predict the properties of nuclear few- and many-body systems. We review the basic methods and several theoretical and algorithmic advances that have been used to further our understanding of atomic nuclei.

   ↳ nucl-thhep-latnucl-exAnn.Rev.Nucl.Part.Sci.(2025)·38 citations
10. 10*

    Bell Inequality Violation of Light Quarks in Back-to-Back Dihadron Pair Production at Lepton Colliders

    Kun Cheng🇺🇸 · Bin Yan🇨🇳

    Spin correlations between particles produced at colliders provide valuable insights for quantum information studies. While traditional studies of quantum information at colliders are typically limited to massive particles with perturbative decay, we propose an innovative method to explore the Bell inequality in massless quark pair systems by analyzing the azimuthal correlations in back-to-back ${\pi }^{+}{\pi }^{-}$ dihadron pair production at lepton colliders. Revisiting the Belle data, we have shown the potential to detect Bell inequality violation of light quarks by introducing an additional angular cut, achieving a significance of 2.5 $\sigma$ even in the worst-case scenario of 100% correlated systematic uncertainties in each bins. The significance substantially exceeds $5\sigma$ when considering uncorrelated systematic uncertainties. Our approach opens avenues for exploring spin quantum information in the non-perturbative aspect and leverages existing data for quantum information research.

    ↳ hep-phhep-exnucl-exnucl-thPRL(2025)·62 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.