Abstract
The first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented. The measurement is performed using jets with p_{T}^{jet}>60 GeV/c and D^{0} mesons with p_{T}^{D}>4 GeV/c in lead-lead (Pb-Pb) and proton-proton (pp) collisions at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=5.02 TeV, recorded by the CMS detector at the LHC. The radial distribution of D^{0} mesons with respect to the jet axis is sensitive to the production mechanisms of the meson, as well as to the energy loss and diffusion processes undergone by its parent parton inside the strongly interacting medium produced in Pb-Pb collisions. When compared to MonteCarlo event generators, the radial distribution in pp collisions is found to be well described by pythia, while the slope of the distribution predicted by sherpa is steeper than that of the data. In Pb-Pb collisions, compared to the pp results, the D^{0} meson distribution for 4<p_{T}^{D}<20 GeV/c hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions. At higher p_{T}^{D}, the Pb-Pb and pp radial distributions are found to be similar.
Highlights
The first study of charm quark diffusion with respect to the jet axis in heavy ion collisions is presented
The measurement is performed using jets with pjTet > 60 GeV=c and D0 mesons with pDT > 4 GeV=c in pleaffisffidffiNffi-ffiNffilffie1⁄4ad5(.0P2b-TPebV),arnedcoprdroetdobny-ptrhoetoCnM(pSpd)etceoctlolirsiaotntsheaLt HaCn.uTchleeorna-dniuaclldeiosntricbeuntitoenr-ooff-mDa0sms eesnoenrsgywiothf respect to the jet axis is sensitive to the production mechanisms of the meson, as well as to the energy loss and diffusion processes undergone by its parent parton inside the strongly interacting medium produced in
In Pb-Pb collisions, compared to the pp results, the D0 meson distribution for 4 < pDT < 20 GeV=c hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions
Summary
(Received 4 November 2019; revised 28 May 2020; accepted 5 August 2020; published 3 September 2020). In Pb-Pb collisions, compared to the pp results, the D0 meson distribution for 4 < pDT < 20 GeV=c hints at a larger distance on average with respect to the jet axis, reflecting a diffusion of charm quarks in the medium created in heavy ion collisions. One of the most striking features of jet quenching is the enhanced production of low transverse momentum hadrons (pT ≈ 2–5 GeV=c) at large angles with respect to the final-state jet axis This phenomenon manifests itself in the form of modifications of the jet fragmentation function [11,12,13], as well as the jet radial profile and the energy flow [14,15,16,17]. The observable is the normalized radial distribution of the D0 meson with respect to the jet axis, defined as
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