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Observation of medium induced modifications of jet fragmentation in PbPb collisions using isolated-photon-tagged jets

The CMS collaboration
No Journal Information, 2018

Abstract
Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and PbPb collisions. The analysis uses data collected with the CMS detector at the CERN LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Fragmentation functions are obtained for jets with p$_\mathrm{T}^\text{jet} >$ 30 GeV in events containing an isolated photon with p$_\mathrm{T}^\gamma>$ 60 GeV, using charged tracks with transverse momentum p$_\mathrm{T}^\text{trk} >$ 1 GeV in a cone around the jet axis. The association with an isolated photon constrains the initial p$_\mathrm{T}$ and azimuthal angle of the parton whose shower produced the jet. For central PbPb collisions, modifications of the jet fragmentation functions are observed when compared to those measured in pp collisions, while no significant differences are found in the 50% most peripheral collisions. Jets in central PbPb events show an excess (depletion) of low (high) p$_\mathrm{T}$ particles, with a transition around 3 GeV.

  • Table 1

    Data from top panel of Fig. 1

    10.17182/hepdata.80817.v1/t1

    $\xi^\mathrm{jet}$ distributions for jets associated with an isolated photon in pp and 50-100% centrality PbPb collisions. The resolutions of the...

  • Table 2

    Data from top panel of Fig. 1

    10.17182/hepdata.80817.v1/t2

    $\xi^\mathrm{jet}$ distributions for jets associated with an isolated photon in pp and 30-50% centrality PbPb collisions. The resolutions of the...

  • Table 3

    Data from top panel of Fig. 1

    10.17182/hepdata.80817.v1/t3

    $\xi^\mathrm{jet}$ distributions for jets associated with an isolated photon in pp and 10-30% centrality PbPb collisions. The resolutions of the...

  • Table 4

    Data from top panel of Fig. 1

    10.17182/hepdata.80817.v1/t4

    $\xi^\mathrm{jet}$ distributions for jets associated with an isolated photon in pp and 0-10% centrality PbPb collisions. The resolutions of the...

  • Table 5

    Data from bottom panel of Fig. 1

    10.17182/hepdata.80817.v1/t5

    PbPb / pp ratio of $\xi^\mathrm{jet}$ distributions for 50-100% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 6

    Data from bottom panel of Fig. 1

    10.17182/hepdata.80817.v1/t6

    PbPb / pp ratio of $\xi^\mathrm{jet}$ distributions for 30-50% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 7

    Data from bottom panel of Fig. 1

    10.17182/hepdata.80817.v1/t7

    PbPb / pp ratio of $\xi^\mathrm{jet}$ distributions for 10-30% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 8

    Data from bottom panel of Fig. 1

    10.17182/hepdata.80817.v1/t8

    PbPb / pp ratio of $\xi^\mathrm{jet}$ distributions for 0-10% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 9

    Data from top panel of Fig. 2

    10.17182/hepdata.80817.v1/t9

    $\xi^\gamma_{\mathrm{T}}$ distributions for jets associated with an isolated photon in pp and 50-100% centrality PbPb collisions. The resolutions of the...

  • Table 10

    Data from top panel of Fig. 2

    10.17182/hepdata.80817.v1/t10

    $\xi^\gamma_{\mathrm{T}}$ distributions for jets associated with an isolated photon in pp and 30-50% centrality PbPb collisions. The resolutions of the...

  • Table 11

    Data from top panel of Fig. 2

    10.17182/hepdata.80817.v1/t11

    $\xi^\gamma_{\mathrm{T}}$ distributions for jets associated with an isolated photon in pp and 10-30% centrality PbPb collisions. The resolutions of the...

  • Table 12

    Data from top panel of Fig. 2

    10.17182/hepdata.80817.v1/t12

    $\xi^\gamma_{\mathrm{T}}$ distributions for jets associated with an isolated photon in pp and 0-10% centrality PbPb collisions. The resolutions of the...

  • Table 13

    Data from bottom panel of Fig. 2

    10.17182/hepdata.80817.v1/t13

    PbPb / pp ratio of $\xi^\gamma_{\mathrm{T}}$ distributions for 50-100% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 14

    Data from bottom panel of Fig. 2

    10.17182/hepdata.80817.v1/t14

    PbPb / pp ratio of $\xi^\gamma_{\mathrm{T}}$ distributions for 30-50% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 15

    Data from bottom panel of Fig. 2

    10.17182/hepdata.80817.v1/t15

    PbPb / pp ratio of $\xi^\gamma_{\mathrm{T}}$ distributions for 10-30% centrality collisions. The resolutions of the measured jet energy and azimuthal...

  • Table 16

    Data from bottom panel of Fig. 2

    10.17182/hepdata.80817.v1/t16

    PbPb / pp ratio of $\xi^\gamma_{\mathrm{T}}$ distributions for 0-10% centrality collisions. The resolutions of the measured jet energy and azimuthal...

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