System size dependence of nuclear modification and azimuthal anisotropy of jet quenching

Abstract

We investigate the system size dependence of jet-quenching by analyzing transverse momentum spectra of neutral pions in Au+Au and Cu+Cu collisions at $\sqrt{s_{\text{NN}}}$ =200 GeV for different centralities. The fast partons are assumed to lose energy by radiating gluons as they traverse the plasma and undergo multiple collisions. The energy loss per collision, $\epsilon$, is taken as proportional to $E$(where $E$ is the energy of the parton), proportional to $\sqrt{E}$, or a constant depending on whether the formation time of the gluon is less than the mean path, greater than the mean free path but less than the path length, or greater than the path length of the partons, respectively. NLO pQCD is used to evaluate pion production by modifying the fragmentation function to account for the energy loss. We reproduce the nuclear modification factor $R_{\text{AA}}$ by treating $\epsilon$ as the only free parameter, depending on the centrality and the mechanism of energy loss. These values are seen to explain the nuclear modification of prompt photons, caused by the energy lost by final state quarks before they fragment into photons. These also reproduce the azimuthal asymmetry of transverse momentum distribution for pions within a factor of two and for prompt photons in a fair agreement with experimental data.

26 pages, 17 figures. One more figure added. Discussion expanded. Typographical corrections done, several references added. To appear in Journal of Physics G

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Cited by in corpus (4)

• Photon production from Pb+Pb collisions at {$\sqrt{s_{\mathrm{NN}}}$} = 5.02 TeV at LHC and at {$\sqrt{s_{\mathrm{NN}}}$} = 39 TeV at FCC
• Understanding partonic energy loss from measured light charged particles and jets in PbPb collisions at LHC energies
• Quantifying the Jet Energy Loss in Pb+Pb collisions at LHC
• Empirical determination of the energy loss of heavy quarks in nuclear collisions at RHIC and LHC energies