Mon·Sep 18, 2023Monday·September 18, 2023

1. 01*

   $\psi$(2S) production in Pb-Pb collisions measured by ALICE at the LHC

   Victor Feuillard (for the ALICE collaboration)🇩🇪

   Charmonium production is a probe sensitive to deconfinement in nucleus-nucleus collisions. The production of J/$\psi$ via regeneration within the QGP or at the phase boundary has been identified as an important ingredient for the description of the observed J/$\psi$ nuclear modification factor at the LHC. The $\psi (2S)$ production relative to J/$\psi$ is a possible discriminator between the two regeneration scenarios. Studies of $\psi (2S)$ production in central nucleus-nucleus collisions at low transverse momentum ($p_{\mathrm{T}}$) are crucial, particularly at the LHC, where regeneration appears to be dominant. A significant $\psi$(2S) signal is extracted at low $p_{\mathrm{T}}$ and forward rapidity in the dimuon decay channel for the first time. This measurement relies on the $\psi (2S)$ cross section measured recently in pp collisions at $\sqrt{s_{}}=5.02$ TeV with an unprecedented precision compared to previous ALICE results. In this contribution, we present newly published results on the $\psi (2S)$-to-J/$\psi$ ratio and the $\psi (2S)$ nuclear modification factor in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV. Results are reported as a function of centrality and $p_{\mathrm{T}}$ for $p_{\mathrm{T}}<12$ GeV/c and are compared to available NA50 and CMS measurements. Comparisons to transport and statistical hadronization model predictions are also provided to shed light on the charmonium states recombination mechanism

   nucl-exPoS(2024)·1 citation
2. 02*

   Investigating radial flow-like effects via pseudorapidity and transverse spherocity dependence of particle production in pp collisions at the LHC

   Aswathy Menon Kavumpadikkal Radhakrishnan🇮🇳 · Suraj Prasad🇮🇳 · Sushanta Tripathy🇨🇭 · Neelkamal Mallick🇮🇳 · Raghunath Sahoo🇮🇳

   Recent observations of quark-gluon plasma (QGP) like signatures in high multiplicity proton-proton (pp) collisions, have compelled the heavy-ion physics community to re-examine small collision systems for proper baseline studies. Event-shape-based studies in pp collisions have succeeded to a certain extent in identifying the rare events mimicking such heavy-ion-like behaviour. In this study, we incorporate PYTHIA8 and AMPT to study radial flow-like signatures in pp collisions at $\sqrt{s}=13$ TeV as a function of transverse spherocity and pseudorapidity. The selection of softer events possibly carrying heavy-ion-like features is performed using the transverse spherocity event-shape observable. As the particle production mechanism in midrapidity differs greatly from the forward rapidity, a pseudorapidity-dependent study is meaningful. Keeping ALICE 3 upgrades at the LHC in mind, this study aims to demonstrate the transverse spherocity and pseudorapidity dependence of the mean transverse momentum, particle ratios, and kinetic freezeout parameters in pp collisions at $\sqrt{s}$ = 13 TeV using PYTHIA8. We observe that the isotropic events show enhanced radial-flow effects in all multiplicity classes, however, the jetty events show signatures of the radial flow-like effects only in high-multiplicity events. For the first time, we show the transverse spherocity and pseudorapidity dependence of partonic modification factor in pp collisions, which clearly shows that by choosing transverse spherocity, one can directly probe the radial flow-like effects in pp collisions at the LHC.

   ↳ hep-phhep-exnucl-exnucl-thEur.Phys.J.Plus(2025)·8 citations
3. 03*

   Evolution of $N=20,28,50$ shell closures in the $20⩽Z⩽30$ region in deformed relativistic Hartree-Bogoliubov theory in continuum

   Ru-You Zheng🇨🇳 · Xiang-Xiang Sun🇨🇳 · Guo-fang Shen · Li-Sheng Geng🇨🇳

   Magicity, or shell closure, plays an important role in our understanding of complex nuclear phenomena. In this work, we employ one of the state-of-the-art density functional theories, the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) with the density functional PC-PK1, to investigate the evolution of the $N=20,28,50$ shell closures in the $20⩽Z⩽30$ region. We show how these three conventional shell closures evolve from the proton drip line to the neutron drip line by studying the charge radii, two-neutron separation energies, two-neutron gaps, quadrupole deformations, and single-particle levels. In particular, we find that in the $21⩽Z⩽27$ region, the $N=50$ shell closure disappears or becomes quenched, mainly due to the deformation effects. Similarly, both experimental data and theoretical predictions indicate that the $N=28$ shell closure disappears in the Mn isotopic chain, also predominantly due to the deformation effects. The DRHBc theory predicts the existence of the $N=20$ shell closure in the Ca, Sc, and Ti isotopic chains, but the existing data for the Ti isotopes suggests the contrary, and therefore more investigations are needed.

   ↳ nucl-thnucl-exCPC(2024)·15 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.