Fri·Feb 24, 2023Friday·February 24, 2023

1. 01*

   Microsecond Isomer at the N=20 Island of Shape Inversion Observed at FRIB

   T. J. Gray🇺🇸 · J. M. Allmond🇺🇸 · Z. Xu🇺🇸 · T. T. King🇺🇸 · R. S. Lubna🇺🇸 · H. L. Crawford🇺🇸 · V. Tripathi🇮🇳 · B. P. Crider · R. Grzywacz🇺🇸 · S. N. Liddick🇺🇸 · A. O. Macchiavelli🇺🇸 · T. Miyagi🇨🇦 and 54 other authors

   Excited-state spectroscopy from the first Facility for Rare Isotope Beams (FRIB) experiment is reported. A 24(2)-$\mu$s isomer was observed with the FRIB Decay Station initiator (FDSi) through a cascade of 224- and 401-keV $\gamma$ rays in coincidence with ${}^{32}\text{Na}$ nuclei. This is the only known microsecond isomer ($1\mu \text{s}\le T_{1/2}<1\text{ ms}$) in the region. This nucleus is at the heart of the $N=20$ island of shape inversion and is at the crossroads of spherical shell-model, deformed shell-model, and ab initio theories. It can be represented as the coupling of a proton hole and neutron particle to ${}^{32}\text{Mg}$, ${}^{32}\text{Mg}+{\pi }^{-1}+{\nu }^{+1}$. This odd-odd coupling and isomer formation provides a sensitive measure of the underlying shape degrees of freedom of ${}^{32}\text{Mg}$, where the onset of spherical-to-deformed shape inversion begins with a low-lying deformed $2^{+}$ state at 885 keV and a low-lying shape-coexisting $0_2^{+}$ state at 1058 keV. We suggest two possible explanations for the 625-keV isomer in ${}^{32}$Na: a $6^{-}$ spherical shape isomer that decays by $E2$ or a $0^{+}$ deformed spin isomer that decays by $M2$. The present results and calculations are most consistent with the latter, indicating that the low-lying states are dominated by deformation.

   nucl-exPRL(2023)·24 citations
2. 02*

   Event plane determination from Zero Degree Calorimeter at the Cooling-Storage-Ring External-target Experiment

   Li-Ke Liu · Hua Pei · Yaping Wang · Biao Zhang · Nu Xu · Shusu Shi

   The Cooling-Storage-Ring External-target Experiment (CSR-CEE) is a spectrometer to study the nature of nuclear matter created in heavy ion collision at $\sqrt{s_{NN}}=$ 2.1 - 2.4 GeV, aiming to reveal Quantum Chromodynamics (QCD) phase structure in the high-baryon density region. Collective flow is regarded as an effective probe for studying the properties of the medium in high-energy nuclear collisions. One of the main functions of the Zero-Degree Calorimeter (ZDC), a sub-detector system in CEE, is to determine the reaction-plane in heavy ion collisions, which is crucial for the measurements of collective flow and other reaction plane related analysis. In this paper, we illustrate the procedures of event plane determination from ZDC. Finally, predictions of the rapidity dependence of directed and elliptic flow for $p$, $d$, $t$, ${}^3$He and ${}^4$He, from 2.1 GeV U+U collisions of IQMD model calculations, are presented.

   nucl-exNucl.Sci.Tech.(2023)·15 citations
3. 03*

   Elliptic flow of identified hadrons in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$ using the PHSD model

   B. Towseef🇮🇳 · M. Farooq🇮🇳 · V. Bairathi🇨🇱 · B. Waseem🇮🇳 · S. Kabana🇨🇱 · S. Ahmad🇮🇳

   We present elliptic flow ($v_2$) of identified hadrons at mid-rapidity ($|y|<1.0$) in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$ using the Parton Hadron String Dynamics (PHSD) model. Transverse momentum ($p_{\mathrm{T}}$) dependence of identified hadron $v_2$ in minimum bias (0-80%) and three different centrality intervals (0-10%, 10-40%, and 40-80%) are presented. A clear centrality dependence of $v_2(p_{\mathrm{T}})$ is observed for particles and anti-particles in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$. We also present $p_{\mathrm{T}}$ dependence of $v_2$ difference ($\mathrm{\Delta }{v}_2$) between particles and corresponding antiparticles. A significant difference in $v_2$ values for baryons and anti-baryons is observed. The number of constituent quark (NCQ) scaling of $v_2$ is discussed in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$. We also present ratio of $v_2(p_{\mathrm{T}})$ between the HSD and PHSD modes to explore the effect of hadronic and partonic interactions in the medium. We observe higher $v_2$ in PHSD mode than the HSD mode, which suggests the formation of partonic medium in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$. These predictions are useful for the interpretation of data measured in Beam Energy Scan (BES) program at RHIC and will be useful for the future Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR).

   nucl-exhep-phnucl-thEPJC(2023)·2 citations
4. 04*

   Elliptic flow of inclusive charged hadrons in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$ using the PHSD model

   Waseem Bhat🇮🇳 · M. Farooq Mir🇮🇳 · Vipul Bairathi🇨🇱 · Towseef Bhat🇮🇳 · Sonia Kabana🇨🇱 · Shabir Bhat🇮🇳

   Elliptic flow ($v_2$) measurements of inclusive charged hadrons at mid-rapidity ($|\eta |<$ 1.0) in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$ using the Parton Hadron String Dynamics (PHSD) model are presented as a function of centrality, transverse momentum ($p_{\mathrm{T}}$) and pseudo-rapidity ($\eta$). The $v_2$ results are obtained using the $\eta$-sub event plane method with respect to event plane angle (${\psi }_2$) and participant plane angle (${\psi }_2^{PP}$). $p_{\mathrm{T}}$-integrated charged hadron $v_2$ shows a strong centrality dependence in Au+Au collisions at $E_{lab}=35\mathrm{A}\mathrm{GeV}$. The eccentricity scaled elliptic flow ($v_2/{\epsilon }_2$) also shows centrality dependence. The higher values of $v_2/{\epsilon }_2$ in central collisions suggest development of stronger collectivity. The measurements are compared with the results from Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}=7.7\mathrm{GeV}$ published by the STAR experiment at RHIC. We also compare results of HSD and PHSD modes of the model to investigate contribution of hadronic and partonic phases of the medium on the measured $v_2$. The current results serve as a prediction of the collective behavior of the matter produced in baryon rich and moderate temperature conditions for the upcoming Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR). These predictions are also useful for the interpretation of data measured at RHIC Beam Energy Scan (BES) program.

   nucl-exhep-phnucl-thJ.Phys.G(2023)·1 citation
5. 05*

   Regeneration of bottomonia in an open quantum systems approach

   Nora Brambilla🇩🇪 · Miguel Ángel Escobedo🇪🇸 · Ajaharul Islam🇺🇸 · Michael Strickland🇺🇸 · Anurag Tiwari🇺🇸 · Antonio Vairo🇩🇪 · Peter Vander Griend🇺🇸

   We demonstrate the importance of quantum jumps in the nonequilibrium evolution of bottomonium states in the quark-gluon plasma. Based on nonrelativistic effective field theory and the open quantum system framework, we evolve the density matrix of color singlet and octet pairs. We show that quantum regeneration of singlet states from octet configurations is necessary to understand experimental results for the suppression of both bottomonium ground and excited states. The values of the heavy-quarkonium transport coefficients used are consistent with recent lattice QCD determinations.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2023)·51 citations
6. 06*

   Probing chiral-even and chiral-odd leading twist quark generalised parton distributions through the exclusive photoproduction of a $\gamma \rho$ pair

   Goran Duplančić🇭🇷 · Saad Nabeebaccus🇫🇷 · Kornelija Passek-Kumerički🇭🇷 · Bernard Pire🇫🇷 · Lech Szymanowski🇵🇱 · Samuel Wallon🇫🇷

   We extend our studies of a new class of $2\to 3$ exclusive processes using the collinear factorisation framework by considering the exclusive photoproduction of a $\gamma \rho$ pair, in the kinematics where the pair has a large invariant mass, {and the outgoing $\rho$-meson has a sufficiently large transverse momentum to not resonate with the nucleon}. We cover the whole kinematical range from medium energies in fixed target experiments to very large energies of colliders, by considering the experimental conditions of JLab~12-GeV, COMPASS, future EIC and LHC (in ultra-peripheral collisions) cases. One of the main interest in studying the present process is that it provides access to both chiral-even and chiral-odd GPDs, depending on the polarisation of the outgoing $\rho$-meson, both at leading twist. Our analysis covers both neutral and charged $\rho$-mesons. We find that the order of magnitude of the obtained cross sections are sufficiently large for a dedicated experimental analysis to be performed, especially at JLab, for both longitudinally and transversely polarised $\rho$. Furthermore, we compute the linear photon beam polarisation asymmetry {which is} sizeable for a longitudinally polarised meson. These predictions are obtained for both asymptotic distribution amplitude (DA) and the \textit{holographic} DA.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2023)·44 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.