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}

p p

data, both at

\sqrt{s_{NN}} = 5.02

TeV, with the ATLAS detector. The process

p p \to γ

+jet+

X

and its analogue in Pb+Pb collisions is measured in events containing an isolated photon with transverse momentum (

p_{T}

) above

50

GeV and reported as a function of jet

p_{T}

. This selection results in a sample of jets with a steeply falling

p_{T}

distribution that are mostly initiated by the showering of quarks. The

p p

and Pb+Pb measurements are used to report the nuclear modification factor,

R_{AA}

, and the fractional energy loss,

S_{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_{AA}

and

S_{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 $p_{T}$ 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 $p_{T}$ 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 $p_{T}$ for different centrality intervals.
Figure 7

Data from Figure 7 in the paper

10.17182/hepdata.139723.v1/t4

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

Data from Figure 9 (right panel) in the paper

10.17182/hepdata.139723.v1/t5

The double $R_{AA}$ ratio of $R_{AA}^{γ -jet} / R_{AA}^{inclusive jet}$ as a function of jet $p_{T}$ .
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 $p_{T}$ 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 $p_{T}$ 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 $p_{T}$ 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 $Δ p_{T}$ of photon-tagged jets as a function of jet $p_{T}$ .
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 $R_{CP}$ of photon-tagged jets as a function of jet $p_{T}$ .

Figure 3

Figure 4

Figure 5

Figure 7

Figure 9

Auxiliary Figure 2

Auxiliary Figure 3

Auxiliary Figure 4

Auxiliary Figure 6

Auxiliary Figure 7

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