Mon·Mar 21, 2022Monday·March 21, 2022

1. 01*

   Measurements of second-harmonic Fourier coefficients from azimuthal anisotropies in $p$$+$$p$, $p$$+$Au, $d$$+$Au, and ${}^3$He$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV

   N.J. Abdulameer · U. Acharya · A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · M. Alfred · V. Andrieux · K. Aoki · N. Apadula · H. Asano · C. Ayuso and 382 other authors

   Recently, the PHENIX Collaboration has published second- and third-harmonic Fourier coefficients $v_2$ and $v_3$ for midrapidity ($|\eta |<0.35$) charged hadrons in 0\%--5\% central $p$$+$Au, $d$$+$Au, and ${}^3$He$+$Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV utilizing three sets of two-particle correlations for two detector combinations with different pseudorapidity acceptance [Phys. Rev. C {\bf 105}, 024901 (2022)]. This paper extends these measurements of $v_2$ to all centralities in $p$$+$Au, $d$$+$Au, and ${}^3$He$+$Au collisions, as well as $p$$+$$p$ collisions, as a function of transverse momentum ($p_T$) and event multiplicity. The kinematic dependence of $v_2$ is quantified as the ratio $R$ of $v_2$ between the two detector combinations as a function of event multiplicity for $0.5$$<$$p_T$$<$$1$ and $2$$<$$p_T$$<$$2.5$ GeV/$c$. A multiphase-transport (AMPT) model can reproduce the observed $v_2$ in most-central to midcentral $d$$+$Au and ${}^3$He$+$Au collisions. However, the AMPT model systematically overestimates the measurements in $p$$+$$p$, $p$$+$Au, and peripheral $d$$+$Au and ${}^3$He$+$Au collisions, indicating a higher nonflow contribution in AMPT than in the experimental data. The AMPT model fails to describe the observed $R$ for $0.5$$<$$p_T$$<$$1$ GeV/$c$, but there is qualitative agreement with the measurements for $2$$<$$p_T$$<$$2.5$ GeV/$c$.

   nucl-exPRC(2023)·25 citations
2. 02*

   Scaling properties of background- and chiral-magnetically-driven charge separation in heavy ion collisions at ${\sqrt{s}}_{\mathrm{NN}}=200$ GeV

   Roy A. Lacey (1) · Niseem Magdy (2) · Petr Parfenov (3) · Arkadiy Taranenko (3) ((1) Depts. of Chemistry and Physics, Stony Brook University, Stony Brook, New York, USA (2) Department of Physics, University of Illinois at Chicago, Chicago, Illinois, USA (3) National Research Nuclear University MEPhI, Moscow, Russia)

   The Anomalous Viscous Fluid Dynamics model, AVFD, is used in concert with the charge-sensitive correlator $R_{{\Psi }_2}(\Delta S)$ to investigate the scaling properties of background- and chiral-magnetically-driven (CME) charge separation ($\Delta S$), characterized by the inverse variance ${\sigma }_{{\mathrm{R}}_{{\mathrm{\Psi }}_2}}^{-2}$ of the $R_{{\Psi }_2}(\Delta S)$ distributions obtained in collisions at ${\sqrt{s}}_{\mathrm{NN}}=200$ GeV. The ${\sigma }_{{\mathrm{R}}_{{\mathrm{\Psi }}_2}}^{-2}$ values for the background are observed to be event-shape-independent. However, they scale with the reciprocal charged-particle multiplicity $(1/⟨N_{\mathrm{ch}}⟩)$, indicating an essential constraint for discerning background from the signal and a robust estimate of the difference between the backgrounds in Ru+Ru and Zr+Zr collisions. By contrast, the ${\sigma }_{{\mathrm{R}}_{{\mathrm{\Psi }}_2}}^{-2}$values for signal + background show characteristic $1/⟨N_{\mathrm{ch}}⟩$ scaling violations that characterize the CME-driven contributions. Corrections to recent $R_{{\Psi }_2}(\Delta S)$ measurements \cite{STAR:2021mii} that account for the background difference in Ru+Ru and Zr+Zr collisions indicate a charge separation difference compatible with the CME. The results further suggest that ${\sigma }_{{\mathrm{R}}_{{\mathrm{\Psi }}_2}}^{-2}$ measurements for peripheral and central collisions in concert with $1/⟨N_{\mathrm{ch}}⟩$ scaling, provides a robust constraint to quantify the background and aid characterization of the CME.

   nucl-exhep-exhep-phnucl-th6 citations
3. 03*

   A Facility for Low-Radioactivity Underground Argon

   Henning O. Back🇺🇸 · Walter Bonivento🇮🇹 · Mark Boulay🇨🇦 · Eric Church🇺🇸 · Steven R. Elliott🇺🇸 · Federico Gabriele🇮🇹 · Cristiano Galbiati🇺🇸 · Graham K. Giovanetti🇺🇸 · Christopher Jackson🇺🇸 · Art McDonald🇨🇦 · Andrew Renshaw🇺🇸 · Roberto Santorelli🇪🇸 and 4 other authors

   The DarkSide-50 experiment demonstrated the ability to extract and purify argon from deep underground sources and showed that the concentration of ${}^{39}$Ar in that argon was greatly reduced from the level found in argon derived from the atmosphere. That discovery broadened the physics reach of argon-based detector and created a demand for low-radioactivity underground argon (UAr) in high-energy physics, nuclear physics, and in environmental and allied sciences. The Global Argon Dark Matter Collaboration (GADMC) is preparing to produce UAr for DarkSide-20k, but a general UAr supply for the community does not exist. With the proper resources, those plants could be operated as a facility to supply UAr for most of the experiments after the DarkSide 20k production. However, if the current source becomes unavailable, or UAr masses greater than what is available from the current source is needed, then a new source must be found. To find a new source will require understanding the production of the radioactive argon isotopes underground in a gas field, and the ability to measure ${}^{37}$Ar, ${}^{39}$Ar, and ${}^{42}$Ar to ultra-low levels. The operation of a facility creates a need for ancillary systems to monitor for ${}^{37}$Ar, ${}^{39}$Ar, or ${}^{42}$Ar infiltration either directly or indirectly, which can also be used to vet the ${}^{37}$Ar, ${}^{39}$Ar, and ${}^{42}$Ar levels in a new UAr source, but requires the ability to separate UAr from the matrix well gas. Finding methods to work with industry to find gas streams enriched in UAr, or to commercialize a UAr facility, are highly desirable.

   ↳ physics.ins-dethep-exnucl-ex10 citations
4. 04*

   $\beta$ decay and evolution of low-lying structure in Ge and As nuclei

   Kosuke Nomura🇭🇷

   A simultaneous calculation for the shape evolution and the related spectroscopic properties of the low-lying states, and the $\beta$-decay properties in the even- and odd-mass Ge and As nuclei in the mass $A\approx 70-80$ region, within the framework of the nuclear density functional theory and the particle-core coupling scheme, is presented. The constrained self-consistent mean-field calculations using a universal energy density functional (EDF) and a pairing interaction determines the interacting-boson Hamiltonian for the even-even core nuclei, and the essential ingredients of the particle-boson interactions for the odd-nucleon systems, and of the Gamow-Teller and Fermi transition operators. A rapid structural evolution from $\gamma$-soft oblate to prolate shapes, as well as the spherical-oblate shape coexistence around the neutron sub-shell closure $N=40$, is suggested to occur in the even-even Ge nuclei. The predicted low-energy spectra, electromagnetic transition rates, and $\beta$-decay $\log ft$ values are in a reasonable agreement with experiment. The predicted $\log ft$ values reflect the structures of the wave functions for the initial and final nuclei of $\beta$ decay, which are, to a large extent, determined by the microscopic input provided by the underlying EDF calculation.

   ↳ nucl-thnucl-exPRC(2022)·13 citations
5. 05*

   Probing neutron-skin thickness with free spectator neutrons in ultracentral high-energy isobaric collisions

   Lu-Meng Liu🇨🇳 · Chun-Jian Zhang🇺🇸 · Jia Zhou🇨🇳 · Jun Xu🇨🇳 · Jiangyong Jia🇺🇸 · Guang-Xiong Peng🇨🇳

   We show that the yield ratio of free spectator neutrons produced in high-energy ${}^{96}$Zr+${}^{96}$Zr to ${}^{96}$Ru+${}^{96}$Ru collisions is a clean probe of the neutron-skin thickness of colliding nuclei and the slope parameter $L$ of the symmetry energy. The idea is demonstrated based on the proton and neutron density distributions via a state-of-the-art Skyrme-Hartree-Fock-Bogolyubov calculation. Among spectator nucleons given by the Glauber model, free spectator neutrons include those from direct production that survive from clusterization as well as those from deexcitation of heavy clusters described by the popular GEMINI model. More free neutrons are produced in collisions of ${}^{96}$Zr nucleus due to its larger neutron skin, compared to those produced in collisions of ${}^{96}$Ru nucleus with a smaller neutron skin. The difference of the free spectator neutron yield is further increased with the increasing difference of the neutron-skin thickness between ${}^{96}$Zr and ${}^{96}$Ru with a larger $L$ value, and the increase in ultracentral collisions is particularly insensitive to model details and experimental uncertainties. Since the production of free spectator neutrons is not affected by the complicated dynamics in the mid-rapidity region, the ratio of their multiplicities in ultracentral isobaric collisions is a robust observable for constraining the neutron skin and $L$ value.

   ↳ nucl-thhep-exnucl-exPLB(2022)·39 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.