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Measurement of the splitting function in pp and PbPb collisions at $\sqrt{s_{_{\mathrm{NN}}}}=$ 5.02 TeV

The collaboration
No Journal Information, 2017

Abstract
Data from heavy ion collisions suggest that the evolution of a parton shower is modified by interactions with the color charges in the dense partonic medium created in these collisions. However, the stage in the shower evolution at which the modifications occur is not known. By removing the soft wide-angle radiation inside a jet, the two leading partons can be resolved as subjets. The momentum ratio of these subjets provides information about the corresponding partons at an early stage of the shower. This substructure observable, known as the splitting function, relates to the process of a parton splitting into two other partons. The measurement is performed for jets with transverse momentum larger than 140 GeV and smaller than 500 GeV, using pp and PbPb collision samples collected by the CMS detector at a center-of-mass energy of 5.02 GeV per nucleon pair. In central PbPb collisions, the splitting function is observed to be modified toward a more unbalanced momentum ratio compared to peripheral PbPb and pp collisions. The measurements are compared to the predictions from event generators and analytical calculations using various models for the medium modification of the jet evolution.

• #### Table 1

Data from Figure 1. Page 3 of preprint

10.17182/hepdata.79666.v1/t1

Groomed jet energy fraction in pp and PbPb collisions for jets with PTJET 160-180 GeV.

• #### Table 2

Data from Figure 2. Page 4 of preprint

10.17182/hepdata.79666.v1/t2

Self-normalized zg distribution in pp collisions for jets with PTJET 160-180 GeV.

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Data from Figure 3a. Page 5 of preprint

10.17182/hepdata.79666.v1/t3

Self-normalized zg distributions in PbPb and smeared pp collisions in the 50-80 centrality event class for jets with PTJET 160-180...

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Data from Figure 3b. Page 5 of preprint

10.17182/hepdata.79666.v1/t4

Self-normalized zg distributions in PbPb and smeared pp collisions in the 30-50 centrality event class for jets with PTJET 160-180...

• #### Table 5

Data from Figure 3c. Page 5 of preprint

10.17182/hepdata.79666.v1/t5

Self-normalized zg distributions in PbPb and smeared pp collisions in the 10-30 centrality event class for jets with PTJET 160-180...

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Data from Figure 3d. Page 5 of preprint

10.17182/hepdata.79666.v1/t6

Self-normalized zg distributions in PbPb and smeared pp collisions in the 0-10 centrality event class for jets with PTJET 160-180...

• #### Table 7

Data from Figure 3e. Page 5 of preprint

10.17182/hepdata.79666.v1/t7

Ratio of zg distributions in PbPb and smeared pp collisions in the 50-80 centrality event class for jets with PTJET...

• #### Table 8

Data from Figure 3f. Page 5 of preprint

10.17182/hepdata.79666.v1/t8

Ratio of zg distributions in PbPb and smeared pp collisions in the 30-50 centrality event class for jets with PTJET...

• #### Table 9

Data from Figure 3g. Page 5 of preprint

10.17182/hepdata.79666.v1/t9

Ratio of zg distributions in PbPb and smeared pp collisions in the 10-30 centrality event class for jets with PTJET...

• #### Table 10

Data from Figure 3h. Page 5 of preprint

10.17182/hepdata.79666.v1/t10

Ratio of zg distributions in PbPb and smeared pp collisions in the 0-10 centrality event class for jets with PTJET...

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Data from Figure 4a. Page 6 of preprint

10.17182/hepdata.79666.v1/t11

Ratio of zg distributions in PbPb and smeared pp collisions in the 10% most central events for jets with PTJET...

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Data from Figure 4b. Page 6 of preprint

10.17182/hepdata.79666.v1/t12

Ratio of zg distributions in PbPb and smeared pp collisions in the 10% most central events for jets with PTJET...

• #### Table 13

Data from Figure 4c. Page 6 of preprint

10.17182/hepdata.79666.v1/t13

Ratio of zg distributions in PbPb and smeared pp collisions in the 10% most central events for jets with PTJET...

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Data from Figure 4d. Page 6 of preprint

10.17182/hepdata.79666.v1/t14

Ratio of zg distributions in PbPb and smeared pp collisions in the 10% most central events for jets with PTJET...

• #### Table 15

Data from Figure 4e. Page 6 of preprint

10.17182/hepdata.79666.v1/t15

Ratio of zg distributions in PbPb and smeared pp collisions in the 10% most central events for jets with PTJET...

• #### Table 16

Data from Figure 4f. Page 6 of preprint

10.17182/hepdata.79666.v1/t16

Ratio of zg distributions in PbPb and smeared pp collisions in the 10% most central events for jets with PTJET...