Measurement of quark- and gluon-like jet fractions using jet charge in PbPb and pp collisions at 5.02 TeV
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Springer
Received: April 1, Revised: May 26, Accepted: May 29, Published: July 17,
2020 2020 2020 2020
The CMS collaboration E-mail: [email protected] Abstract: The momentum-weighted sum of the electric charges of particles inside a jet, known as jet charge, is sensitive to the electric charge of the particle initiating the parton √ shower. This paper presents jet charge distributions in sNN = 5.02 TeV lead-lead (PbPb) and proton-proton (pp) collisions recorded with the CMS detector at the LHC. These data correspond to integrated luminosities of 404 µb−1 and 27.4 pb−1 for PbPb and pp collisions, respectively. Leveraging the sensitivity of the jet charge to fundamental differences in the electric charges of quarks and gluons, the jet charge distributions from simulated events are used as templates to extract the quark- and gluon-like jet fractions from data. The modification of these jet fractions is examined by comparing pp and PbPb data as a function of the overlap of the colliding Pb nuclei (centrality). This measurement tests the color charge dependence of jet energy loss due to interactions with the quark-gluon plasma. No significant modification between different centrality classes and with respect to pp results is observed in the extracted quark- and gluon-like jet fractions. Keywords: Hadron-Hadron scattering (experiments), Heavy-ion collision, Jets ArXiv ePrint: 2004.00602
Open Access, Copyright CERN, for the benefit of the CMS Collaboration. 3 Article funded by SCOAP .
https://doi.org/10.1007/JHEP07(2020)115
JHEP07(2020)115
Measurement of quark- and gluon-like jet fractions using jet charge in PbPb and pp collisions at 5.02 TeV
Contents 1
2 The CMS detector
2
3 Event selection and simulated event samples
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4 Jet and track reconstruction
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5 Jet charge measurement
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6 Corrections for background and detector effects
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7 Template fitting
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8 Systematic uncertainties
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9 Results
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10 Summary
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A Jet charge measurements
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The CMS collaboration
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1
Introduction
High-momentum partons produced by hard scatterings in heavy ion collisions undergo energy loss as they traverse the quark-gluon plasma (QGP) created in these interactions [1]. The mechanisms by which these partons lose energy to the medium, as well as their color dependence, are still not fully understood [2, 3]. The particles resulting from the fragmentation and hadronization of these partons can be clustered into jets. Jets are used as parton proxies to examine the properties of the QGP. Parton energy loss manifests itself in various experimental observables including the suppression of high transverse momentum (pT ) hadrons and jets [4–8], as well as modifications of parton showers [9, 10]. These phenomena are collectively referred to as jet quenching [1]. At leading order in quantum chromodynamics, the type of parton that initiates a jet can be distinguished. The resulting jet can therefore be labeled as a quark, antiquark, or gluon jet. Several recent measurements indicate that the fractions
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