Mon·Mar 9, 2015Monday·March 9, 2015

1. 01*

   Probing Properties of Hot and Dense QCD Matter with Heavy Flavor in the PHENIX Experiment at RHIC

   Rachid Nouicer (for the PHENIX Collaboration)🇺🇸

   Hadrons carrying heavy quarks, i.e. charm or bottom, are important probes of the hot and dense medium created in relativistic heavy ion collisions. Heavy quark-antiquark pairs are mainly produced in initial hard scattering processes of partons. While some of the produced pairs form bound quarkonia, the vast majority hadronize into particles carrying open heavy flavor. Heavy quark production has been studied by the PHENIX experiment at RHIC via measurements of single leptons from semi-leptonic decays in both the electron channel at mid-rapidity and in the muon channel at forward rapidity. A large suppression and azimuthal anisotropy of single electrons have been observed in Au+Au collisions at 200 GeV. These results suggest a large energy loss and flow of heavy quarks in the hot, dense matter. The PHENIX experiment has also measured $J/\psi$ production at $\sqrt{s_{nn}}$ = 200 GeV in p+p, d+Au, Cu+Cu and Au+Au collisions, both at mid- and forward-rapidities, and additionally Cu+Au and U+U at forward-rapidities. In the most energetic collisions, more suppression is observed at forward rapidity than at central rapidity. This can be interpreted either as a sign of quark recombination, or as a hint of additional cold nuclear matter effects. The centrality dependence of nuclear modification factor, RAA, for $J/\psi$ in U+U collisions at $\sqrt{s_{nn}}$ = 193 GeV shows a similar trend to the lighter systems, Au+Au and Cu+Cu, at similar energy 200 GeV.

   nucl-exEPJ Web Conf.(2015)·0 citations
2. 02*

   Measurement of (alpha,n) reaction cross sections of erbium isotopes for testing astrophysical rate predictions

   G. G Kiss🇭🇺 · T. Szücs🇭🇺 · T. Rauscher🇬🇧 · Zs Török🇭🇺 · L. Csedreki🇮🇹 · Zs Fülöp🇭🇺 · Gy Gyürky🇭🇺 · Z. Halász🇭🇺

   The $\gamma$-process in core-collapse and/or type Ia supernova explosions is thought to explain the origin of the majority of the so-called $p$ nuclei (the 35 proton-rich isotopes between Se and Hg). Reaction rates for $\gamma$-process reaction network studies have to be predicted using Hauser-Feshbach statistical model calculations. Recent investigations have shown problems in the prediction of $\alpha$-widths at astrophysical energies which are an essential input for the statistical model. It has an impact on the reliability of abundance predictions in the upper mass range of the $p$ nuclei. With the measurement of the ${}^{164,166}$Er($\alpha$,n)${}^{167,169}$Yb reaction cross sections at energies close to the astrophysically relevant energy range we tested the recently suggested low energy modification of the $\alpha$+nucleus optical potential in a mass region where $\gamma$-process calculations exhibit an underproduction of the $p$ nuclei. Using the same optical potential for the $\alpha$-width which was derived from combined ${}^{162}$Er($\alpha$,n) and ${}^{162}$Er($\alpha$,$\gamma$) measurement makes it plausible that a low-energy modification of the optical $\alpha$+nucleus potential is needed.

   nucl-exJ.Phys.G(2015)·15 citations
3. 03*

   Recent results on event-by-event fluctuations in ALICE at the LHC

   Nirbhay Kumar Behera (for the ALICE Collaboration)🇮🇳

   Non-statistical event-by-event fluctuations in relativistic heavy-ion collisions have been proposed as a probe of the phase transition of hadronic matter to a deconfined phase of quarks and gluons, the so-called Quark-Gluon Plasma. In a thermodynamical picture of the strongly interacting system formed in heavy-ion collisions, the dynamical fluctuations of net-charge, fluctuations of the mean transverse momentum, mean multiplicity and balance functions are related to the fundamental properties of the system, hence they may reveal information about the QCD phase transition. In this article, recent results on event-by-event measurements of net-charge fluctuations, the measurement of the balance function and mean transverse momentum fluctuations are discussed.

   ↳ hep-exnucl-exPoS(2015)·0 citations
4. 04*

   QCD description of backward vector meson hard electroproduction

   B. Pire🇫🇷 · K. Semenov-Tian-Shansky🇧🇪 · L. Szymanowski🇵🇱

   We consider backward vector meson exclusive electroproduction off nucleons in the framework of collinear QCD factorization. Nucleon to vector meson transition distribution amplitudes arise as building blocks for the corresponding factorized amplitudes. In the near-backward kinematics, the suggested factorization mechanism results in the dominance of the transverse cross section of vector meson production (${\sigma }_T\gg {\sigma }_L$) and in the characteristic $1/Q^8$-scaling behavior of the cross section. We evaluate nucleon to vector meson TDAs in the cross-channel nucleon exchange model and present estimates of the differential cross section for backward ${\rho }^0$, $\omega$ and $\varphi$ meson production off protons. The resulting cross sections are shown to be measurable in the forthcoming JLab@12 GeV experiments.

   ↳ hep-phhep-exnucl-exnucl-thPRD(2015)·21 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.