Observation of medium-induced modifications of Jet fragmentation in Pb-Pb collisions at sNN =5.02 TeV using isolated photon-tagged jets
Measurements of fragmentation functions for jets associated with an isolated photon are presented for the first time in pp and Pb-Pb 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 ar...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English English |
| Published: |
American Physical Society
2018
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| Subjects: | |
| Online Access: | http://irep.iium.edu.my/70737/ http://irep.iium.edu.my/70737/ http://irep.iium.edu.my/70737/ http://irep.iium.edu.my/70737/1/70737_Observation%20of%20Medium-Induced%20Modifications_article.pdf http://irep.iium.edu.my/70737/2/70737_Observation%20of%20Medium-Induced%20Modifications_scopus_new.pdf |
| Summary: | Measurements of fragmentation functions for jets associated with an isolated photon are presented for
the first time in pp and Pb-Pb 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 pjet
T > 30 GeV=c in events containing an isolated photon with pγ
T > 60 GeV=c, using charged
tracks with transverse momentum ptrk
T > 1 GeV=c in a cone around the jet axis. The association with an
isolated photon constrains the initial pT and azimuthal angle of the parton whose shower produced the jet.
For central Pb-Pb 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 Pb-Pb events show an excess (depletion) of low (high) pT particles, with a
transition around 3 GeV=c. This measurement shows for the first time the in-medium shower modifications
of partons (quark dominated) with well-defined initial kinematics. It constitutes a new well-controlled
reference for testing theoretical models of the parton passage through the quark-gluon plasma. |
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