Thu·Mar 29, 2018Thursday·March 29, 2018

1. 01*

   Azimuthally-differential pion femtoscopy relative to the third harmonic event plane in Pb-Pb collisions at $\sqrt{{\text{s}}_{{}_{\mathrm{NN}}}}$ = 2.76 TeV

   ALICE Collaboration

   Azimuthally-differential femtoscopic measurements, being sensitive to spatio-temporal characteristics of the source as well as to the collective velocity fields at freeze out, provide very important information on the nature and dynamics of the system evolution. While the HBT radii oscillations relative to the second harmonic event plane measured recently reflect mostly the spatial geometry of the source, model studies have shown that the HBT radii oscillations relative to the third harmonic event plane are predominantly defined by the velocity fields. In this Letter, we present the first results on azimuthally-differential pion femtoscopy relative to the third harmonic event plane as a function of the pion pair transverse momentum $k_{\mathrm{T}}$ for different collision centralities in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV. We find that the $R_{\mathrm{side}}$ and $R_{\mathrm{out}}$ radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate in phase relative to the third harmonic event plane, similar to the results from 3+1D hydrodynamical calculations. The observed radii oscillations unambiguously signal a collective expansion and anisotropy in the velocity fields. A comparison of the measured radii oscillations with the Blast-Wave model calculations indicate that the initial state triangularity is washed-out at freeze out.

   nucl-exhep-exPLB(2018)·13 citations
2. 02*

   Study of Isolated-photon and Jet Momentum Imbalance in $pp$ and $PbPb$ collisions

   Lin Chen🇨🇳 · Guang-You Qin🇨🇳 · Lei Wang🇨🇳 · Shu-Yi Wei🇨🇳 · Bo-Wen Xiao🇨🇳 · Han-Zhong Zhang🇨🇳 · Ya-Qi Zhang🇨🇳

   In this paper, we study the production of isolated-photon plus a jet in $pp$ and $PbPb$ collisions, which can be used as an important probe to the jet transport property in quark gluon plasma created in heavy ion collisions. Normally, there are two types of observables associated with the production of isolated-photon plus a jet, namely, the azimuthal angular correlation and the transverse momentum imbalance. To understand both observables in the full kinematical region, we need to employ the perturbative QCD calculation, which takes into account the hard splitting of partons, together with the Sudakov resummation formalism, which resums soft gluon splittings. Furthermore, by introducing energy-loss into the system, we calculate the enhancement of the momentum imbalance distribution for $AA$ as compared to $pp$ collisions and make predictions for future unfolded experimental data. In addition, in order to extract the jet transport coefficient more precisely in our numerical calculation, we also distinguish quark jets from gluon jets, since they interact with quark gluon plasma with different strengths. This work provides a reliable theoretical tool for the calculation of the gamma-jet correlation, which can lead us to a more precise extraction of the jet transport coefficient in relativistic heavy-ion collisions.

   ↳ hep-phnucl-exnucl-thNPB(2018)·34 citations
3. 03*

   Influence of anisotropic $\Lambda /\Sigma$ creation on the ${\Xi }^{-}$ mutiplicity in subthreshold proton-nucleus collisions

   Miklós Zétényi🇭🇺 · György Wolf🇭🇺

   We present an analysis of ${\Xi }^{-}$ baryon production in subthreshold proton--nucleus ($p+A$) collisions in the framework of a BUU type transport model. We propose a new mechanism for $\Xi$ production in the collision of a secondary $\Lambda$ or $\Sigma$ hyperon and a nucleon from the target nucleus. We find that the ${\Xi }^{-}$ multiplicity in $p+A$ collisions is sensitive to the angular distribution of hyperon production in the primary $N+N$ collision. Using reasonable assumptions on the unknown elementary cross sections we are able to reproduce the ${\Xi }^{-}$ multiplicity and the ${\Xi }^{-}/(\Lambda +{\Sigma }^0)$ ratio obtained in the HADES experiment in $p$+Nb collisions at $\sqrt{s_{NN}}=$ 3.2 GeV energy.

   ↳ nucl-thnucl-exPLB(2018)·11 citations
4. 04*

   Photonuclear Reactions in Astrophysics

   T. Rauscher🇬🇧

   A brief overview of the importance of photodisintegration reactions in astrophysical environments is given and the relevance of photonuclear experiments for nucleosynthesis studies is discussed.

   ↳ astro-ph.HEnucl-exnucl-thNucl.Phys.News(2018)·11 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.