Study of Jet Quenching in Quark Gluon Plasma Using Jet Charge Measurements

The properties of quark-gluon plasma (QGP) are studied using jets, which are collimated streams of hadrons produced by fragmentation of high transverse momentum quarks and gluons from hard scatterings in the early phase of heavy-ion collisions. These hard-scattered quarks and gluons subsequently traverse and interact with the QGP, losing energy. This phenomenon is referred to as jet quenching. The jets are thus used as in-situ probes to analyze the rich dynamics of the QGP medium. Recent calculations from models operating at different energy scales predict varying magnitudes of color-charge dependence for the jet-medium interactions. In this work, the properties of the QGP are further explored using jet charge measurements in 5.02 TeV PbPb collisions recorded with the CMS detector along with pp data at the same energy. Jet charge is defined as the momentum-weighted sum of electric charges of particles inside a jet. The sensitivity of the jet charge to the electric charge of the initiating parton can be leveraged to discriminate between quark- and gluon-jets. A template-fitting method is presented to extract the quark- and gluon-jet fractions in pp and PbPb collisions using jet charge templates from simulations. The first jet charge measurement in heavy-ion collisions is carried out in this work and can provide further constraints to theoretical models describing the QGP, including the color charge dependence of jet quenching.