Mon·Mar 30, 2020Monday·March 30, 2020

1. 01*

   Measurement of cumulants of conserved charge multiplicity distributions in Au+Au collisions from the STAR experiment

   Ashish Pandav (for the STAR Collaboration)🇮🇳

   We report the collision-centrality dependence of cumulants of event-by-event net-proton, net-charge and net-kaon distributions in Au+Au collisions for center-of-mass energy $\sqrt{s_{NN}}$ = 54.4 GeV from the STAR experiment. Strong collision-centrality dependence is observed for cumulants ($C_n,n$ $\le$ 4) of the net-particle distributions. The cumulant ratios $C_3/C_2$, $C_4/C_2$ and $C_6/C_2$ exhibit a weak collision-centrality dependence. The $C_6/C_2$ of net-proton and net-charge distributions for most central gold nuclei collisions at $\sqrt{s_{NN}}$ = 54.4 GeV show positive sign while they remain negative at 200 GeV for the same collision system. To understand effects of acceptance and baryon number conservation, the measurements are compared to expectations from the UrQMD and HIJING models calculated within the STAR detector acceptance.

   nucl-exNPA(2021)·14 citations
2. 02*

   Reexamination of ${}^6$Li scattering as a Probe to Investigate the Isoscalar Giant Resonances in Nuclei

   J. C. Zamora🇧🇷 · C. Sullivan🇺🇸 · R.G.T. Zegers🇺🇸 · N. Aoi🇯🇵 · L. Batail🇫🇷 · D. Bazin🇺🇸 · M. Carpenter🇺🇸 · J.J. Carroll🇺🇸 · I. Deloncle🇫🇷 · Y.D. Fang🇨🇳 · H. Fujita🇯🇵 · U. Garg🇺🇸 and 28 other authors

   Inelastic ${}^6$Li scattering at 100 MeV/u on ${}^{12}$C and ${}^{93}$Nb have been measured with the high-resolution magnetic spectrometer Grand Raiden. The magnetic-rigidity settings of the spectrometer covered excitation energies from 10 to 40 MeV and scattering angles in the range $0^{\circ }<{\theta }_{\text{lab.}}<2^{\circ }$. The isoscalar giant monopole resonance was selectively excited in the present data. Measurements free of instrumental background and the very favorable resonance-to-continuum ratio of ${}^6$Li scattering allowed for precise determination of the $E0$ strengths in ${}^{12}$C and ${}^{93}$Nb. It was found that the monopole strength in ${}^{12}$C exhausts $52\pm 3^{\text{(stat.)}}\pm 8^{\text{(sys.)}}$\% of the energy-weighted sum rule (EWSR), which is considerably higher than results from previous $\alpha$-scattering experiments. The monopole strength in ${}^{93}$Nb exhausts $92\pm 4^{\text{(stat.)}}\pm 10^{\text{(sys.)}}$\% of the EWSR, and it is consistent with measurements of nuclei with mass number of $A\approx 90$. Such comparison indicates that the isoscalar giant monopole resonance distributions in these nuclei are very similar, and no influence due to nuclear structure was observed.

   nucl-exnucl-thPRC(2020)·5 citations
3. 03*

   Results on Total and Elastic Cross Sections in Proton-Proton Collisions at $\sqrt{s}=200$ GeV

   STAR Collaboration: J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson · A. Aparin · E. C. Aschenauer · M. U. Ashraf and 352 other authors

   We report results on the total and elastic cross sections in proton-proton collisions at $\sqrt{s}=200$ GeV obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section was measured in the squared four-momentum transfer range $0.045\le -t\le 0.135$ GeV${}^2$. The value of the exponential slope parameter $B$ of the elastic differential cross section $d\sigma /dt\sim e^{-Bt}$ in the measured $-t$ range was found to be $B=14.32\pm 0.09(stat.{)}_{-0.28}^{+0.13}(syst.)$ GeV${}^{-2}$. The total cross section ${\sigma }_{tot}$, obtained from extrapolation of the $d\sigma /dt$ to the optical point at $-t=0$, is ${\sigma }_{tot}=54.67\pm 0.21(stat.{)}_{-1.38}^{+1.28}(syst.)$ mb. We also present the values of the elastic cross section ${\sigma }_{el}=10.85\pm 0.03(stat.{)}_{-0.41}^{+0.49}(syst.)$ mb, the elastic cross section integrated within the STAR $t$-range ${\sigma }_{el}^{det}=4.05\pm 0.01(stat.{)}_{-0.17}^{+0.18}(syst.)$ mb, and the inelastic cross section ${\sigma }_{inel}=43.82\pm 0.21(stat.{)}_{-1.44}^{+1.37}(syst.)$ mb. The results are compared with the world data.

   ↳ hep-exnucl-exPLB(2020)·41 citations
4. 04*

   Anomalous chiral transports and spin polarization in heavy-ion collisions

   Yu-Chen Liu🇨🇳 · Xu-Guang Huang🇨🇳

   Relativistic heavy-ion collisions create hot quark-gluon plasma as well as very strong electromagnetic (EM) and fluid vortical fields. The strong EM field and vorticity can induce intriguing macroscopic quantum phenomena such as chiral magnetic, chiral separation, chiral electric separation, and chiral vortical effects as well as the spin polarization of hadrons. These phenomena provide us with experimentally feasible means to study the nontrivial topological sector of quantum chromodynamics, the possible parity violation of strong interaction at high temperature, and the subatomic spintronics of quark-gluon plasma. These studies, both in theory and in experiments, are strongly connected with other subfields of physics such as condensed matter physics, astrophysics, and cold atomic physics, and thus form an emerging interdisciplinary research area. We give an introduction to the aforementioned phenomena induced by the EM field and vorticity and an overview of the current status of their experimental research in heavy-ion collisions. We also briefly discuss spin hydrodynamics as well as chiral and spin kinetic theories.

   ↳ nucl-thhep-phnucl-exNucl.Sci.Tech.(2020)·120 citations
5. 05*

   Nonperturbative Effects on Radiative Energy Loss of Heavy Quarks

   Shuai Y.F. Liu🇺🇸 · Ralf Rapp🇺🇸

   The radiative energy loss of fast partons traveling through the quark-gluon plasma (QGP) is commonly studied within perturbative QCD (pQCD). Nonperturbative (NP) effects, which are expected to become important near the critical temperature, have been much less investigated. Here, we utilize a recently developed $T$-matrix approach to incorporate NP effects for gluon emission off heavy quarks propagating through the QGP. We set up four cases that contain, starting from a Born diagram calculation with color-Coulomb interaction, an increasing level of NP components, by subsequently including (remnants of) confining interactions, resummation in the heavy-light scattering amplitude, and off-shell spectral functions for both heavy and light partons. For each case we compute the power spectra of the emitted gluons, heavy-quark transport coefficients (drag and transverse-momentum broadening, $\hat{q}$), and the path-length dependent energy loss within a "QGP brick" at fixed temperature. Investigating the differences in these quantities between the four cases illustrates how NP mechanisms affect gluon radiation processes. While the baseline perturbative processes experience a strong suppression of soft radiation due to thermal masses of the emitted gluons, confining interactions, ladder resummations and broad spectral functions (re-)generate a large enhancement toward low momenta and low temperatures. For example, for a 10 GeV charm quark at 200 MeV temperature, they enhance the transport coefficients by up to a factor of 10, while the results smoothly converge to perturbative results at sufficiently hard scales.

   ↳ nucl-thhep-phnucl-exJHEP(2020)·23 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.