Search results for "relativistic heavy ion collisions"
showing 3 items of 3 documents
Centrality, rapidity and transverse momentum dependence of J/ψ suppression in Pb-Pb collisions at root(NN)-N-S=2.76TeV
2014
The inclusive J/ψ nuclear modification factor (RAA) in Pb–Pb collisions at √sNN=2.76TeVhas been measured by ALICE as a function of centrality in the e+e−decay channel at mid-rapidity (|y| <0.8) and as a function of centrality, transverse momentum and rapidity in the μ+μ−decay channel at forward-rapidity (2.5 <y <4). The J/ψyields measured in Pb–Pb are suppressed compared to those in ppcollisions scaled by the number of binary collisions. The RAAintegrated over a centrality range corresponding to 90% of the inelastic Pb–Pb cross section is 0.72 ±0.06(stat.) ±0.10(syst.)at mid-rapidity and 0.58 ±0.01(stat.) ±0.09(syst.)at forward-rapidity. At low transverse momentum, significantly larger valu…
A first estimate of $\eta/s$ in Au+Au reactions at E$_{\rm lab}=1.23$ $A$GeV
2020
The HADES experiment at GSI has recently provided data on the flow coefficients $v_1,...,v_4$ for protons in Au+Au reactions at $E_{\rm lab} = 1.23$~$A$GeV (or $\sqrt{s_\mathrm{NN}}=2.4$ GeV). This data allows to estimate the shear viscosity over entropy ratio, $\eta/s$ at low energies via a coarse graining analysis of the UrQMD transport simulations of the flow harmonics in comparison to the experimental data. By this we can provide for the first time an estimate of $\eta/s\approx0.65\pm0.15$ (or $(8\pm2)\,(4\pi)^{-1}$) at such low energies.
Measurement of photon?jet transverse momentum correlations in 5.02 TeV Pb + Pb and pp collisions with ATLAS
2019
Jets created in association with a photon can be used as a calibrated probe to study energy loss in the medium created in nuclear collisions. Measurements of the transverse momentum balance between isolated photons and inclusive jets are presented using integrated luminosities of 0.49 nb−1 of Pb + Pb collision data at TeV and 25 pb−1 of pp collision data at TeV recorded with the ATLAS detector at the LHC. Photons with transverse momentum GeV and are paired with all jets in the event that have GeV and pseudorapidity . The transverse momentum balance given by the jet-to-photon ratio, , is measured for pairs with azimuthal opening angle . Distributions of the per-photon jet yield as a function…