Parton energy loss in the quark-gluon plasma (QGP) is studied with ameasurement of photon-tagged jet production in 1.7 nb$^{-1}$ of Pb+Pb data and260 pb$^{-1}$ of $pp$ data, both at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, with theATLAS detector. The process $pp \to \gamma$+jet+$X$ and its analogue in Pb+Pbcollisions is measured in events containing an isolated photon with transversemomentum ($p_\mathrm{T}$) above $50$ GeV and reported as a function of jet$p_\mathrm{T}$. This selection results in a sample of jets with a steeplyfalling $p_\mathrm{T}$ distribution that are mostly initiated by the showeringof quarks. The $pp$ and Pb+Pb measurements are used to report the nuclearmodification factor, $R_\mathrm{AA}$, and the fractional energy loss,$S_\mathrm{loss}$, for photon-tagged jets. In addition, the results arecompared with the analogous ones for inclusive jets, which have a significantlysmaller quark-initiated fraction. The $R_\mathrm{AA}$ and $S_\mathrm{loss}$values are found to be significantly different between those for photon-taggedjets and inclusive jets, demonstrating that energy loss in the QGP is sensitiveto the colour-charge of the initiating parton. The results are also comparedwith a variety of theoretical models of colour-charge-dependent energy loss.
Comparison of inclusive and photon-tagged jet suppression in 5.02 TeV Pb+Pb collisions with ATLAS
Capua, M;Mastroberardino, A;Meoni, E;Schioppa, M;Tassi, E;
2023-01-01
Abstract
Parton energy loss in the quark-gluon plasma (QGP) is studied with ameasurement of photon-tagged jet production in 1.7 nb$^{-1}$ of Pb+Pb data and260 pb$^{-1}$ of $pp$ data, both at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, with theATLAS detector. The process $pp \to \gamma$+jet+$X$ and its analogue in Pb+Pbcollisions is measured in events containing an isolated photon with transversemomentum ($p_\mathrm{T}$) above $50$ GeV and reported as a function of jet$p_\mathrm{T}$. This selection results in a sample of jets with a steeplyfalling $p_\mathrm{T}$ distribution that are mostly initiated by the showeringof quarks. The $pp$ and Pb+Pb measurements are used to report the nuclearmodification factor, $R_\mathrm{AA}$, and the fractional energy loss,$S_\mathrm{loss}$, for photon-tagged jets. In addition, the results arecompared with the analogous ones for inclusive jets, which have a significantlysmaller quark-initiated fraction. The $R_\mathrm{AA}$ and $S_\mathrm{loss}$values are found to be significantly different between those for photon-taggedjets and inclusive jets, demonstrating that energy loss in the QGP is sensitiveto the colour-charge of the initiating parton. The results are also comparedwith a variety of theoretical models of colour-charge-dependent energy loss.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
