Fri·Jan 24, 2025Friday·January 24, 2025

1. 01*

   Direct Measurement of the ${}^{39}$Ar Half-life from 3.4 Years of Data with the DEAP-3600 Detector

   DEAP Collaboration: P. Adhikari🇨🇦 · R. Ajaj🇨🇦 · M. Alpízar-Venegas🇲🇽 · P.-A. Amaudruz🇨🇦 · J. Anstey🇨🇦 · D.J. Auty🇨🇦 · M. Batygov🇨🇦 · B. Beltran🇨🇦 · M.A. Bigentini🇨🇦 · C.E. Bina🇨🇦 · W.M. Bonivento🇮🇹 · M.G. Boulay🇨🇦 and 104 other authors

   The half-life of ${}^{39}$Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 $\pm$ 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of ${}^{39}$Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope's half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of ${}^{39}$Ar decays. Observing over a period of 3.4 years, the ${}^{39}$Ar half-life is measured to be $(302\pm 8_{\mathrm{stat}}\pm 6_{\mathrm{sys}})$ years. This new direct measurement suggests that the half-life of ${}^{39}$Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope's half-life as input.

   nucl-exphysics.ins-detEPJC(2025)·10 citations
2. 02*

   Investigation of Medium Modifications to ${}^{12}$C Structure Functions in the Resonance Region

   S. Alsalmi🇺🇸 · I. Albayrak · A. Ahmidouch · J. Arrington🇺🇸 · A. Asaturyan🇺🇸 · A. Bodek🇺🇸 · P. Bosted🇺🇸 · R. Bradford · E. Brash🇺🇸 · A. Bruell · C Butuceanu · M. E. Christy🇺🇸 and 66 other authors

   We present results from a high precision experimental study of the nuclear modification of the longitudinal ($F_L$) to transverse ($F_1$) structure function ratio for bound nucleons in the resonance region. The inclusive electron scattering cross sections were measured in Jefferson Lab Experimental Hall C on carbon and deuterium nuclei for a large range of kinematics, allowing for separations of the longitudinal and transverse structure functions to be performed at a range of four-momentum transfer values $0.5\le Q^2\le$ 3.75 GeV${}^2$. In contrast to the significant body of measurements of the nuclear modification of the $F_2$ structure function in the deep inelastic scattering region, there is very little on $F_L$ and $R=F_L/2x{F}_1$ in the region of the nucleon resonances. In this paper we present measurements of the nuclear effect on $R$ for ${}^{12}$C ($R_C$) relative to deuterium ($R_D$). These results indicate regions in which in $R_C>R_D$, requiring that the nuclear modifications be different in all three structure functions, $F_2$, $F_1$ and $F_L$.

   nucl-ex0 citations
3. 03*

   Distribution Functions of a Radially Excited Pion

   Z.-N. Xu🇪🇸 · Z.-Q. Yao🇪🇸 · D. Binosi🇮🇹 · M. Ding🇨🇳 · C. D. Roberts🇨🇳 · J. Rodríguez-Quintero🇪🇸

   A nonperturbatively-improved, symmetry-preserving approximation to the quantum field equations relevant in calculations of meson masses and interactions is used to deliver predictions for all distribution functions (DFs) of the ground state pion, ${\pi }_0$, and its first radial excitation, ${\pi }_1$, viz. valence, glue, and sea. Regarding Mellin moments of the valence DFs, the $m=0,1$ moments in both states are identical; but for each $m\ge 2$, that in the ${\pi }_0$ is greater than its partner in the ${\pi }_1$. Working with such information, pointwise reconstructions of the hadron-scale ${\pi }_{0,1}$ valence DFs are developed. The predicted ${\pi }_0$ valence DF is consistent with extant results. The ${\pi }_1$ valence DF is novel: it possesses three-peaks, with the central maximum partnered by secondary peaks on either side, each separated from the centre by a zero: the zeroes lie at $x\approx 0.2,0.8$ and the secondary peaks at $x\approx 0.1,0.9$. Evolution to $\zeta =3.2$GeV, a typical scale for nonperturbative calculations, is accomplished using an evolution scheme for parton DFs that is all-orders exact. At this higher scale, differences between the ${\pi }_{0,1}$ valence DFs remain significant, but analogous differences between glue and sea DFs are far smaller. This analysis shows that, owing to constraints imposed by chiral symmetry and the pattern by which it is broken in Nature, there are noticeable differences between the structural properties of the pion ground state and its radial excitations.

   ↳ hep-phhep-exhep-latnucl-ex+1EPJC(2025)·7 citations
4. 04*

   Polarization-Analyzed Small-Angle Neutron Scattering with an $\text{in-situ}$ ${}^3$He neutron spin filter at the China Spallation Neutron Source

   Long Tian · Han Gao · Tianhao Wang · Haiyun Teng · Jian Tang · Qingbo Zheng · Taisen Zuo · Tengfei Cui · Bin Wang · Xu Qin · Yongxiang Qiu · Yuchen Dong and 6 other authors

   Polarization-analyzed small-angle neutron scattering (PASANS) is an advanced technique that enables the selective investigation of magnetic scattering phenomena in magnetic materials and distinguishes coherent scattering obscured by incoherent backgrounds, making it particularly valuable for cutting-edge research. The successful implementation of PASANS in China was achieved for the first time at the newly commissioned Very Small Angle Neutron Scattering (VSANS) instrument at the China Spallation Neutron Source (CSNS). This technique employs a combination of a double-V cavity supermirror polarizer and a radio frequency (RF) neutron spin flipper to manipulate the polarization of the incident neutrons. The scattered neutron polarization is stably analyzed by a specially designed $\text{in-situ}$ optical pumping ${}^3$He neutron spin filter, which covers a spatially symmetric scattering angle coverage of about 4.8 ${}^{\circ }$. A comprehensive PASANS data reduction method, aimed at pulsed neutron beams, has been established and validated with a silver behenate powder sample, indicating a maximum momentum transfer coverage of approximately 0.25 Å ${}^{-1}$.

   ↳ physics.ins-detnucl-exNucl.Sci.Tech.(2026)·0 citations
5. 05*

   Towards a parameter-free analysis of the QCD chiral phase transition and its universal critical behavior

   Sabarnya Mitra🇩🇪 · Frithjof Karsch🇩🇪

   To quantify the universal properties of chiral phase transition in (2+1)-flavor QCD, we use an improved, renormalized order parameter for the chiral symmetry breaking. We construct ratios of this divergence-free order parameter from its values for different pairs of light quark masses. From this, we determine in a parameter-independent manner, the chiral phase transition temperature $T_c$ and the associated critical exponent $\delta$ of the universality class. We present first numerical results of these calculations on $N_{\tau }=8$ lattices, with staggered fermions.

   ↳ hep-lathep-phnucl-exnucl-thSpringer Proc.Phys.(2026)·4 citations
6. 06*

   The Impact of Helium Exposure on the PMTs of the SuperNEMO Experiment

   SuperNEMO Collaboration: X. Aguerre (1 & 2) · A.S. Barabash (3) · A. Basharina-Freshville (4) · M. Bongrand (5) · Ch. Bourgeois (5) · D. Breton (5) · R. Breier (6) · J. Busto (7) · C. Cerna (1) · M. Ceschia (4) · E. Chauveau (1) · A. Chopra (4) and 67 other authors

   The performance of Hamamatsu 8" photomultiplier tubes (PMTs) of the type used in the SuperNEMO neutrinoless double-beta decay experiment (R5912-MOD), is investigated as a function of exposure to helium (He) gas. Two PMTs were monitored for over a year, one exposed to varying concentrations of He, and the other kept in standard atmospheric conditions as a control. Both PMTs were exposed to light signals generated by a Bi-207 radioactive source that provided consistent large input PMT signals similar to those that are typical of the SuperNEMO experiment. The energy resolution of PMT signals corresponding to 1 MeV energy scale determined from the Bi-207 decay spectrum, shows a negligible degradation with He exposure; however the rate of after-pulsing shows a clear increase with He exposure, which is modelled and compared to diffusion theory. A method for reconstructing the partial pressure of He within the PMT and a method for determining the He breakdown point, are introduced. The implications for long-term SuperNEMO operations are briefly discussed.

   ↳ physics.ins-detnucl-exJINST(2025)·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.