Measurements of electroweak-boson-tagged jet energy loss and modification by ATLAS

Dennis V Perepelitsa

doi:10.1016/j.nuclphysa.2020.121838

Abstract

These proceedings describe the preliminary results from the ATLAS Collaboration at the LHC on Z-tagged charged hadron production in Pb+Pb and pp collisions, presented in a parallel talk at the Quark Matter 2019 conference.

Highlights

Measurements of jets produced in association with a high transverse momentum electroweak boson are an effective way to study partonic energy loss in the Quark Gluon Plasma (QGP) produced in ultrarelativistic heavy ion collisions at the Large Hadron Collider (LHC)
At large pcTh or xhZ, the rate of charged hadrons per Z boson is observed to be significantly suppressed below unity in Pb+Pb collisions compared to that in pp collisions. This suppression is systematically larger in more central events, reaching a minimum of approximately 0.2, and is attributable to the energy loss of the hard-scattered partons produced azimuthally opposite to the Z boson
At low pcTh or xhZ, the IAA values are observed to be enhanced, reaching a factor of approximately two in the kinematic range presented here. This enhancement is compatible with the softening of the parton fragmentation and with a potential contribution from the response of the QGP to the deposited lost energy

Summary

Introduction

Measurements of jets produced in association with a high transverse momentum (pT) electroweak boson are an effective way to study partonic energy loss in the Quark Gluon Plasma (QGP) produced in ultrarelativistic heavy ion collisions at the Large Hadron Collider (LHC). The bosons are not strongly interacting and traverse the QGP unaffected They provide information about the initial hard scattering kinematics, such as the direction, flavor and pT of the outgoing parton, before the parton shower is modified through interactions with the QGP. The larger statistics of the Pb+Pb collision dataset recorded in 2018, as well as improvements to the reconstruction in heavy ion events, have enabled new, detailed measurements of Z-tagged jet modification. Photon- and Z-tagged jet measurements in similar kinematic ranges allows for a comparison of the energy loss for partons with different initial virtualities

Methods

Results

Conclusion