Fri·May 14, 2021Friday·May 14, 2021

1. 01*

   Investigation of Experimental Observables in Search of the Chiral Magnetic Effect in Heavy-ion Collisions in the STAR experiment

   Subikash Choudhury🇨🇳 · Xin Dong🇺🇸 · Jim Drachenberg🇺🇸 · James Dunlop🇺🇸 · ShinIchi Esumi🇯🇵 · Yicheng Feng🇺🇸 · Evan Finch🇺🇸 · Yu Hu🇨🇳 · Jiangyong Jia🇺🇸 · Jerome Lauret🇺🇸 · Wei Li🇺🇸 · Jinfeng Liao🇺🇸 and 18 other authors

   The chiral magnetic effect (CME) is a novel transport phenomenon, arising from the interplay between quantum anomalies and strong magnetic fields in chiral systems. In high-energy nuclear collisions, the CME may survive the expansion of the quark-gluon plasma fireball and be detected in experiments. Over the past decade, the experimental searches for the CME have aroused extensive interest at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC). The main goal of this article is to investigate three pertinent experimental approaches: the $\gamma$ correlator, the $R$ correlator and the signed balance functions. We will exploit both simple Monte Carlo simulations and a realistic event generator (EBE-AVFD) to verify the equivalence in the kernel-component observables among these methods and to ascertain their sensitivities to the CME signal for the isobaric collisions at RHIC.

   nucl-exnucl-thCPC(2022)·47 citations
2. 02*

   Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC

   ALICE Collaboration

   Recent $p_{\mathrm{T}}$-integrated cross section measurements of the ground-state charm mesons and baryons, D${}^0$, D${}^{+}$, D${}_{\mathrm{s}}^{+}$, ${\Lambda }_{\mathrm{c}}^{+}$, and ${\Xi }_{\mathrm{c}}^0$, are used to evaluate the charm fragmentation fractions and production cross section per unit of rapidity at midrapidity ($|y|<0.5$), in pp collisions at $\sqrt{s}=5.02$ TeV at the LHC. The latter is $\mathrm{d}{\sigma }^{\mathrm{c}\overline{\mathrm{c}}}/\mathrm{d}y{|}_{|y|<0.5}$ =1165 $\pm 44(\mathrm{stat}{)}_{-101}^{+134}(\mathrm{syst})$ $\mu b$. These measurements were obtained for the first time in hadronic collisions at the LHC including the charm baryon states, recently measured by ALICE at midrapidity. The charm fragmentation fractions differ significantly from the values measured in e${}^{+}$e${}^{-}$ and ep collisions, providing evidence of the dependence of the parton-to-hadron fragmentation fractions on the collision system, indicating that the assumption of their universality is not supported by the measured cross sections. An increase of a factor of about 3.3 for the fragmentation fraction for the ${\Lambda }_{\mathrm{c}}^{+}$ with a significance of $5\sigma$ between the values obtained in pp collisions and those obtained in e${}^{+}$e${}^{-}$ (ep) collisions is reported. The fragmentation fraction for the ${\Xi }_{\mathrm{c}}^0$ was obtained for the first time in any collision system. The measured fragmentation fractions were used to update the $\mathrm{c}\overline{\mathrm{c}}$ cross sections per unit of rapidity at $|y|<0.5$ at $\sqrt{s}=2.76$ and 7 TeV, which are about 40% higher than the previously published results. The data were compared with perturbative-QCD calculations and lie at the upper edge of the theoretical bands.

   nucl-exhep-exPRD(2022)·167 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.