Abstract

Parton energy loss in the quark-gluon plasma (QGP) is studied with a measurement of photon-tagged jet production in 1.7 nb$^{-1}$ of Pb+Pb data and 260 pb$^{-1}$ of $pp$ data, both at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, with the ATLAS detector. The process $pp \to \gamma$+jet+$X$ and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum ($p_\mathrm{T}$) above $50$ GeV and reported as a function of jet $p_\mathrm{T}$. This selection results in a sample of jets with a steeply falling $p_\mathrm{T}$ distribution that are mostly initiated by the showering of quarks. The $pp$ and Pb+Pb measurements are used to report the nuclear modification factor, $R_\mathrm{AA}$, and the fractional energy loss, $S_\mathrm{loss}$, for photon-tagged jets. In addition, the results are compared with the analogous ones for inclusive jets, which have a significantly smaller quark-initiated fraction. The $R_\mathrm{AA}$ and $S_\mathrm{loss}$ values are found to be significantly different between those for photon-tagged jets and inclusive jets, demonstrating that energy loss in the QGP is sensitive to the colour-charge of the initiating parton. The results are also compared with a variety of theoretical models of colour-charge-dependent energy loss.

Figure 3

Data from Figure 3 in the paper

10.17182/hepdata.139723.v1/t1

The differential cross-section of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ in pp collisions.
Figure 4

Data from Figure 4 in the paper

10.17182/hepdata.139723.v1/t2

The yields of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ in Pb+Pb collisions for different centrality intervals.
Figure 5

Data from Figure 5 in the paper

10.17182/hepdata.139723.v1/t3

The nuclear modification factor of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ for different centrality intervals.
Figure 7

Data from Figure 7 in the paper

10.17182/hepdata.139723.v1/t4

The $\Delta p_{\mathrm{T}}$ of photon-tagged jets as a function of jet $p_{\mathrm{T}}$.
Figure 9

Data from Figure 9 (right panel) in the paper

10.17182/hepdata.139723.v1/t5

The double $R_{\mathrm{AA}}$ ratio of $R_{\mathrm{AA}}^{\gamma\text{-jet}}/R_{\mathrm{AA}}^{\text{inclusive jet}}$ as a function of jet $p_{\mathrm{T}}$.
Auxiliary Figure 2

Data from Auxiliary Figure 2 in https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2022-14/

10.17182/hepdata.139723.v1/t6

The differential cross-section of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ in pp collisions.
Auxiliary Figure 3

Data from Auxiliary Figure 3 in https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2022-14/

10.17182/hepdata.139723.v1/t7

The yields of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ in Pb+Pb collisions for different centrality intervals.
Auxiliary Figure 4

Data from Auxiliary Figure 4 in https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2022-14/

10.17182/hepdata.139723.v1/t8

The nuclear modification factor of photon-tagged jets as a function of jet $p_{\mathrm{T}}$ for different centrality intervals.
Auxiliary Figure 6

Data from Auxiliary Figure 6 in https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2022-14/

10.17182/hepdata.139723.v1/t9

The $\Delta p_{\mathrm{T}}$ of photon-tagged jets as a function of jet $p_{\mathrm{T}}$.
Auxiliary Figure 7

Data from Auxiliary Figure 7 in https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2022-14/

10.17182/hepdata.139723.v1/t10

The $R_{\mathrm{CP}}$ of photon-tagged jets as a function of jet $p_{\mathrm{T}}$.

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Figure 7

Figure 9

Auxiliary Figure 2

Auxiliary Figure 3

Auxiliary Figure 4

Auxiliary Figure 6

Auxiliary Figure 7

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