Evidence of medium response to hard probes using correlations of Z bosons with hadrons in heavy ion collisions

Abstract

The first measurement of pseudorapidity and azimuthal angle distributions relative to the momentum vector of a Z boson for low transverse momentum ($p_{\mathrm{T}}$) charged hadrons in lead-lead (PbPb) collisions is presented. By studying the hadrons produced in an event with a high-$p_{\mathrm{T}}$ Z boson (40 $<$ $p_{\mathrm{T}}$ $<$ 350 GeV), the analysis probes how the quark-gluon plasma (QGP) medium created in these collisions affects the parton recoiling opposite to the Z boson. Utilizing PbPb data at a nucleon-nucleon center-of-mass energy $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 5.02 TeV from 2018 with an integrated luminosity of 1.67 nb${}^{-1}$ and proton-proton (pp) data at the same energy from 2017 with 301 pb${}^{-1}$, the distributions are examined in bins of charged-hadron $p_{\mathrm{T}}$. A significant modification of the distributions for charged hadrons in the range 1 $<$ $p_{\mathrm{T}}$ $<$ 2 GeV in PbPb collisions is observed when compared to reference measurements from pp collisions. The data provide new information about the correlation between hard and soft particles in heavy ion collisions, which can be used to test predictions of various jet quenching models. When compared to theoretical predictions, the results are consistent with expectations of a hydrodynamic wake created when the QGP is depleted of energy by the parton propagating through it. Therefore, this Letter presents the first evidence of probe-induced energy depletion and the resulting response by the QGP medium.

Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-23-006 (CMS Public Pages)

References in corpus (12)

• The automated computation of tree-level and next-to-leading order differential cross sections, and their matching to parton shower simulations
• An Introduction to PYTHIA 8.2
• Measurement of jet suppression in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• The ALICE experiment: a journey through QCD
• A Monte Carlo Model for 'Jet Quenching'
• Heavy quarks and jets as probes of the QGP
• Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions
• Jet quenching pattern at LHC in PYQUEN model
• 3D structure of jet-induced diffusion wake in an expanding quark-gluon plasma
• Overview of high-density QCD studies with the CMS experiment at the LHC
• Disentangling Jet Modification in Jet Simulations and in Z+Jet Data
• Medium Response and Jet-Hadron Correlations in Relativistic Heavy-Ion Collisions

Cited by in corpus (3)

• Observation of the jet diffusion wake using dijets in heavy ion collisions
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• Deriving a parton shower for jet thermalization in QCD plasmas