SearcharxivSearch

arXiv subjects

L. Gaillard

Publications and source records attributed to L. Gaillard.

4 recordsLinked to original sources

Near-side azimuthal and pseudorapidity correlations using neutral strange baryons and mesons in d+Au, Cu+Cu and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV

We present measurements of the near-side of triggered di-hadron correlations using neutral strange baryons ($Λ$, $\barΛ$) and mesons ($K^0_S$) at intermediate transverse momentum (3 $<$ $p_T$ $<$ 6 GeV/$c$) to look for possible flavor and baryon/meson dependence. This study is performed in $d$+Au, Cu+Cu and Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations due to jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.

nucl-ex

System size and energy dependence of near-side di-hadron correlations

Two-particle azimuthal ($Δϕ$) and pseudorapidity ($Δη$) correlations using a trigger particle with large transverse momentum ($p_T$) in $d$+Au, Cu+Cu and Au+Au collisions at $\sqrt{s_{NN}}$ =\xspace 62.4 GeV and 200~GeV from the STAR experiment at RHIC are presented. The \ns correlation is separated into a jet-like component, narrow in both $Δϕ$ and $Δη$, and the ridge, narrow in $Δϕ$ but broad in $Δη$. Both components are studied as a function of collision centrality, and the jet-like correlation is studied as a function of the trigger and associated $p_T$. The behavior of the jet-like component is remarkably consistent for different collision systems, suggesting it is produced by fragmentation. The width of the jet-like correlation is found to increase with the system size. The ridge, previously observed in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV, is also found in Cu+Cu collisions and in collisions at $\sqrt{s_{NN}}$ =\xspace 62.4 GeV, but is found to be substantially smaller at $\sqrt{s_{NN}}$ =\xspace 62.4 GeV than at $\sqrt{s_{NN}}$ = 200 GeV for the same average number of participants ($ \langle N_{\mathrm{part}}\rangle$). Measurements of the ridge are compared to models.

nucl-ex

Beam-Energy and System-Size Dependence of Dynamical Net Charge Fluctuations

We present measurements of net charge fluctuations in $Au + Au$ collisions at $\sqrt{s_{NN}} = $ 19.6, 62.4, 130, and 200 GeV, $Cu + Cu$ collisions at $\sqrt{s_{NN}} = $ 62.4, 200 GeV, and $p + p$ collisions at $\sqrt{s} = $ 200 GeV using the dynamical net charge fluctuations measure $ν_{+-{\rm,dyn}}$. We observe that the dynamical fluctuations are non-zero at all energies and exhibit a modest dependence on beam energy. A weak system size dependence is also observed. We examine the collision centrality dependence of the net charge fluctuations and find that dynamical net charge fluctuations violate $1/N_{ch}$ scaling, but display approximate $1/N_{part}$ scaling. We also study the azimuthal and rapidity dependence of the net charge correlation strength and observe strong dependence on the azimuthal angular range and pseudorapidity widths integrated to measure the correlation.

nucl-ex

Strange baryon resonance production in $\sqrt{s_{NN}} = 200$ GeV $p+p$ and $Au+Au$ collisions

We report the measurements of $Σ(1385)$ and $Λ(1520)$ production in $p+p$ and $Au+Au$ collisions at $\sqrt{s_{NN}} = 200$ GeV from the STAR collaboration. The yields and the $p_{T}$ spectra are presented and discussed in terms of chemical and thermal freeze-out conditions and compared to model predictions. Thermal and microscopic models do not adequately describe the yields of all the resonances produced in central $Au+Au$ collisions. Our results indicate that there may be a time-span between chemical and thermal freeze-out during which elastic hadronic interactions occur.

nucl-ex