Wed·Aug 30, 2017Wednesday·August 30, 2017

1. 01*

   Isothermal compressibility of hadronic matter formed in relativistic nuclear collisions

   Maitreyee Mukherjee🇮🇳 · Sumit Basu🇺🇸 · Arghya Chatterjee🇮🇳 · Sandeep Chatterjee🇵🇱 · Souvik Priyam Adhya🇮🇳 · Sanchari Thakur🇮🇳 · Tapan K. Nayak🇮🇳

   We present the first estimates of isothermal compressibility (\kT) of hadronic matter formed in relativistic nuclear collisions ($\sqrt{s_{\mathrm{NN}}}=7.7$ GeV to 2.76~TeV) using experimentally observed quantities. \kT~is related to the fluctuation in particle multiplicity, temperature, and volume of the system formed in the collisions. Multiplicity fluctuations are obtained from the event-by-event distributions of charged particle multiplicities in narrow centrality bins. The dynamical components of the fluctuations are extracted by removing the contributions to the fluctuations from the number of participating nucleons. From the available experimental data, a constant value of \kT~has been observed as a function of collision energy. The results are compared with calculations from UrQMD, AMPT, and EPOS event generators, and estimations of \kT~are made for Pb-Pb collisions at the CERN Large Hadron Collider. A hadron resonance gas (HRG) model has been used to calculate \kT~as a function of collision energy. Our results show a decrease in \kT~at low collision energies to \sNN~$\sim$~20~GeV, beyond which the \kT~values remain almost constant.

   nucl-exhep-exhep-phnucl-thPLB(2018)·23 citations
2. 02*

   Constraining the Sea Quark Distributions Through W${}^{\pm }$ Cross Section Ratio Measurements at STAR

   M. Posik (for the STAR Collaboration)🇺🇸

   Over the past several years, parton distribution functions (PDFs) have become more precise. However there are still kinematic regions where more data are needed to help constrain global PDF extractions, such as the sea quark distributions $\bar{d}$/$\bar{u}$ near the valence region (Bjorken-x $\approx$ 0.1 - 0.3).~Current measurements appear to suggest different high-x behaviors of these distributions, leading to large uncertainties in global fits. The charged W cross section ratio (W${}^{+}$/W${}^{-}$) is sensitive to the unpolarized $u,d,\bar{u},$ and $\bar{d}$ quark distributions at large $Q^2$ set by the $W$ mass and could help shed light on this discrepancy. The STAR experiment at RHIC is well equipped to measure the leptonic decays of W bosons, in the mid-rapidity range $\left(|\eta |\le 1\right)$, produced in proton+proton collisions at $\sqrt{s}$ = 500/510 GeV. At these kinematics STAR is sensitive to quark distributions near Bjorken-x of 0.16. STAR can also measure the W cross section ratio in a more forward bin ranging from 1.1 $<\eta <$ 2.0, which extends the sea quark sensitivity to higher x. RHIC runs from 2011 through 2013 have collected about 350 pb${}^{-1}$ of integrated luminosity, and a 2017 run is expected to provide an additional 400 pb${}^{-1}$. Presented here are preliminary results for the 2011-2012 charged W cross section ratios ($\sim$100pb${}^{-1}$) and an update on the 2013 charged W cross section analysis ($\sim$250 pb${}^{-1}$).

   nucl-exPoS(2018)·2 citations
3. 03*

   Probing the chiral magnetic wave in pPb and PbPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV using charge-dependent azimuthal anisotropies

   CMS Collaboration

   Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that, at LHC energies, the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

   nucl-exPRC(2019)·46 citations
4. 04*

   New Results on Short-Range Correlations in Nuclei

   Nadia Fomin🇺🇸 · Douglas Higinbotham🇺🇸 · Misak Sargsian🇺🇸 · Patricia Solvignon🇺🇸

   Nuclear dynamics at short distances is one of the most fascinating topics of strong interaction physics. The physics of it is closely related to the understanding the role of the QCD in generating nuclear forces at short distances as well as understanding the dynamics of the super-dense cold nuclear matter relevant to the interior of neutron stars. With an emergence of high energy electron and proton beams there is a significant recent progress in high energy nuclear scattering experiments aimed at studies of short-range structure of nuclei. This in turn stimulated new theoretical studies resulting in the observation of several new phenomena specific to the short range structure of nuclei. In this work we review recent theoretical and experimental progress in studies of short-range correlations in nuclei and their importance for advancing our understanding of the dynamics of nuclear interactions at small distances.

   ↳ nucl-thnucl-exAnn.Rev.Nucl.Part.Sci.(2017)·80 citations
5. 05*

   ${\pi }^0$ and $\eta$ meson production in proton-proton collisions at $\sqrt{s}=8$ TeV

   ALICE Collaboration

   An invariant differential cross section measurement of inclusive ${\pi }^0$ and $\eta$ meson production at mid-rapidity in pp collisions at $\sqrt{s}=8$ TeV was carried out by the ALICE experiment at the LHC. The spectra of ${\pi }^0$ and $\eta$ mesons were measured in transverse momentum ranges of $0.3<p_{\mathrm{T}}<35$ GeV/$c$ and $0.5<p_{\mathrm{T}}<35$ GeV/$c$, respectively. Next-to-leading order perturbative QCD calculations using fragmentation functions DSS14 for the ${\pi }^0$ and AESSS for the $\eta$ overestimate the cross sections of both neutral mesons, although such calculations agree with the measured $\eta /{\pi }^0$ ratio within uncertainties. The results were also compared with PYTHIA~8.2 predictions for which the Monash~2013 tune yields the best agreement with the measured neutral meson spectra. The measurements confirm a universal behavior of the $\eta /{\pi }^0$ ratio seen for NA27, PHENIX and ALICE data for pp collisions from $\sqrt{s}=27.5$ GeV to $\sqrt{s}=8$ TeV within experimental uncertainties. A relation between the ${\pi }^0$ and $\eta$ production cross sections for pp collisions at $\sqrt{s}=8$ TeV is given by $m_{\mathrm{T}}$ scaling for $p_{\mathrm{T}}>3.5$ GeV/$c$. However, a deviation from this empirical scaling rule is observed for transverse momenta below $p_{\mathrm{T}}<3.5$ GeV/$c$ in the $\eta /{\pi }^0$ ratio with a significance of $6.2\sigma$.

   ↳ hep-exnucl-exEPJC(2018)·102 citations
6. 06*

   Recent STAR Jet Results of the High-Energy Spin Physics Program at RHIC

   Daniel L. Olvitt Jr. (for the STAR Collaboration)🇺🇸

   The production of jets from polarized proton+proton collisions at STAR is dominated by quark-gluon and gluon-gluon scattering. The dijet double spin asymmetry (A\tsub{LL}) is sensitive to the polarized gluon distribution ($\Delta g(x)$). Dijets are also advantageous because the parton momentum fraction, x, of initial partons may be reconstructed to first order from the final state measurements. Both jet and dijet A\tsub{LL} measurements at $\sqrt{s}$ = 200 GeV have helped to constrain $\Delta g(x)$ in the range $0.05<x<0.3$. In 2012, data were collected at $\sqrt{s}$ = 510 GeV in order to probe lower values of x, these data are consistent with the $\sqrt{s}$ = 200 GeV results in the overlapping $x_T$ region. Jet and dijet preliminary A\tsub{LL} results have been released and will soon be incorporated into global analyses. In 2013, high luminosity data, with an estimated 250 pb${}^{-1}$ of integrated luminosity were collected at $\sqrt{s}$ = 510 GeV. These data have a figure of merit of $\sim$3 times that of the 2012 data. An update on the dijet A\tsub{LL} measurement will be presented using polarized p+p data collected at STAR during 2013.

   ↳ hep-exnucl-ex0 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.