Wed·May 10, 2017Wednesday·May 10, 2017

1. 01*

   Investigating the Role of Coherence Effects on Jet Quenching in Pb-Pb Collisions at $\sqrt{s_{NN}}=2.76$ TeV using Jet Substructure

   Nima Zardoshti (for the ALICE Collaboration)🇬🇧

   We report measurements of two jet shapes, the ratio of 2-Subjettiness to 1-Subjettiness (${\tau }_2/{\tau }_1$) and the opening angle between the two axes of the 2-Subjettiness jet shape, which is obtained by reclustering the jet with the exclusive-$k_T$ algorithm~\cite{kT} and undoing the final clustering step. The aim of this measurement is to explore a possible change in the rate of 2-pronged objects in Pb-Pb compared to pp due to colour coherence. Coherence effects~\cite{ColourCoherence} relate to the ability of the medium to resolve a jet's substructure, which has an impact on the energy loss magnitude and mechanism of the traversing jet. In both collision systems charged jets are found with the anti-$k_T$ algorithm~\cite{Anti-kT}, a resolution parameter of $R=$0.4\ and a constituent cut off of $0.15$ GeV. This analysis uses hadron-jet coincidence techniques in Pb-Pb collisions to reject the combinatorial background and corrects further for background effects by employing various jet shape subtraction techniques and two dimensional unfolding. Measurements of the Nsubjettiness for jet momenta of $40-60$ GeV/$c$ in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV and pp collisions at $\sqrt{s}=7$ TeV will be presented and compared to PYTHIA simulations.

   nucl-exhep-exNPA(2017)·9 citations
2. 02*

   Modeling pion production in heavy-ion collisions at intermediate energies

   Gao-Chan Yong🇨🇳

   Pion production in nucleus-nucleus collisions at intermediate energies was modeled in the framework of the Isospin-dependent Boltzmann-Uehling-Uhlenbeck (IBUU) transport model. The effects of nucleon-nucleon short-range correlations in initialization and mean-field potential, isospin-dependent in-medium baryon-baryon elastic and inelastic cross sections and pion in-medium effect are all considered in this model. It is found that the ratio and yields of ${\pi }^{-}$and ${\pi }^{+}$ in Au+Au reaction at 400 MeV/nucleon reproduce the FOPI/GSI data very well especially with a soft symmetry energy in the present transport model. Predictions on the single and double ${\pi }^{-}/{\pi }^{+}$ ratio are made for the isotope reaction systems ${}^{132}\mathrm{Sn}{+}^{124}\mathrm{Sn}$ and ${}^{108}\mathrm{Sn}{+}^{112}\mathrm{Sn}$ at 300 MeV/nucleon since related experiments are being carried out at RIKEN/Japan.

   ↳ nucl-thnucl-exPRC(2017)·38 citations
3. 03*

   Dynamical dissociation of quarkonia by wave function decoherence

   Shiori Kajimoto🇯🇵 · Yukinao Akamatsu🇯🇵 · Masayuki Asakawa🇯🇵 · Alexander Rothkopf🇩🇪

   We investigate the real-time evolution of quarkonium bound states in a quark-gluon plasma in one dimension using an improved QCD based stochastic potential model. This model describes the quarkonium dynamics in terms of a Schrödinger equation with an in-medium potential and two noise terms encoding the residual interactions between the heavy quarks and the medium. The probabilities of bound states in a static medium and in a boost-invariantly expanding quark-gluon plasma are discussed. We draw two conclusions from our results: One is that the outcome of the stochastic potential model is qualitatively consistent with the experimental data in relativistic heavy-ion collisions. The other is that the noise plays an important role in order to describe quarkonium dynamics in medium, in particular it causes decoherence of the quarkonium wave function. The effectiveness of decoherence is controlled by a new length scale $l_{\mathrm{corr}}$. It represents the noise correlation length and its effect has not been included in existing phenomenological studies.

   ↳ nucl-thhep-phnucl-exPRD(2018)·90 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.