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Title: Measurement of q ˆ in Relativistic Heavy Ion Collisions using di-hadron correlations

The propagation of partons from hard scattering through the Quark Gluon Plasma produced in A+A collisions at RHIC and the LHC is represented in theoretical analyses by the transport coefficient $$\hat{q}$$ and predicted to cause both energy loss of the outgoing partons, observed as suppression of particles or jets with large transverse momentum p T, and broadening of the azimuthal correlations of the outgoing di-jets or di-hadrons from the outgoing parton-pair, which has not been observed. The widths of azimuthal correlations of di-hadrons with the same trigger particle p Tt and associated p Ta transverse momenta in p+p and Au+Au are so-far statistically indistinguishable as shown in recent as well as older di-hadron measurements and also with jet-hadron and hadron-jet measurements. The azimuthal width of the di-hadron correlations in p+p collisions, beyond the fragmentation transverse momentum, j T, is dominated by k T, the so-called intrinsic transverse momentum of a parton in a nucleon, which can be measured. The broadening should produce a larger k T in A+A than in p+p collisions. The present work introduces the observation that the k T measured in p+p collisions for di-hadrons with p Tt and p Ta must be reduced to compensate for the energy loss of both the trigger and away parent partons when comparing to the k T measured with the same di-hadron p Tt and p Ta in Au+Au collisions. This idea is applied to a recent STAR di-hadron measurement, with result <$$\hat{q}$$L>=2.1±0.6 GeV 2. This is more precise but in agreement with a theoretical calculation of <$$\hat{q}$$L>=14$$+42\atop{-14}$$ GeV 2 using the same data. Assuming a length ≈7 fm for central Au+Au collisions the present result gives $$\hat{q}$$≈0.30±0.09 GeV 2/fm, in fair agreement with the JET collaboration result from single hadron suppression of $$\hat{q}$$≈1.2±0.3 GeV 2/fm at an initial time τ 0=0.6 fm/c in Au+Au collisions at √sNN=200 GeV.
Authors:
 [1]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Report Number(s):
BNL-114100-2017-JA
Journal ID: ISSN 0370-2693
Grant/Contract Number:
SC0012704
Type:
Published Article
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 771; Journal Issue: C; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Research Org:
Brookhaven National Lab. (BNL), Upton, NY (United States). Relativistic Heavy Ion Collider (RHIC)
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS; 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Relativistic Heavy Ion Collider
OSTI Identifier:
1361706
Alternate Identifier(s):
OSTI ID: 1376151

Tannenbaum, M. J.. Measurement of qˆ in Relativistic Heavy Ion Collisions using di-hadron correlations. United States: N. p., Web. doi:10.1016/j.physletb.2017.05.090.
Tannenbaum, M. J.. Measurement of qˆ in Relativistic Heavy Ion Collisions using di-hadron correlations. United States. doi:10.1016/j.physletb.2017.05.090.
Tannenbaum, M. J.. 2017. "Measurement of qˆ in Relativistic Heavy Ion Collisions using di-hadron correlations". United States. doi:10.1016/j.physletb.2017.05.090.
@article{osti_1361706,
title = {Measurement of qˆ in Relativistic Heavy Ion Collisions using di-hadron correlations},
author = {Tannenbaum, M. J.},
abstractNote = {The propagation of partons from hard scattering through the Quark Gluon Plasma produced in A+A collisions at RHIC and the LHC is represented in theoretical analyses by the transport coefficient $\hat{q}$ and predicted to cause both energy loss of the outgoing partons, observed as suppression of particles or jets with large transverse momentum pT, and broadening of the azimuthal correlations of the outgoing di-jets or di-hadrons from the outgoing parton-pair, which has not been observed. The widths of azimuthal correlations of di-hadrons with the same trigger particle pTt and associated pTa transverse momenta in p+p and Au+Au are so-far statistically indistinguishable as shown in recent as well as older di-hadron measurements and also with jet-hadron and hadron-jet measurements. The azimuthal width of the di-hadron correlations in p+p collisions, beyond the fragmentation transverse momentum, jT, is dominated by kT, the so-called intrinsic transverse momentum of a parton in a nucleon, which can be measured. The broadening should produce a larger kT in A+A than in p+p collisions. The present work introduces the observation that the kT measured in p+p collisions for di-hadrons with pTt and pTa must be reduced to compensate for the energy loss of both the trigger and away parent partons when comparing to the kT measured with the same di-hadron pTt and pTa in Au+Au collisions. This idea is applied to a recent STAR di-hadron measurement, with result <$\hat{q}$L>=2.1±0.6 GeV2. This is more precise but in agreement with a theoretical calculation of <$\hat{q}$L>=14$+42\atop{-14}$ GeV2 using the same data. Assuming a length ≈7 fm for central Au+Au collisions the present result gives $\hat{q}$≈0.30±0.09 GeV2/fm, in fair agreement with the JET collaboration result from single hadron suppression of $\hat{q}$≈1.2±0.3 GeV2/fm at an initial time τ0=0.6 fm/c in Au+Au collisions at √sNN=200 GeV.},
doi = {10.1016/j.physletb.2017.05.090},
journal = {Physics Letters. Section B},
number = C,
volume = 771,
place = {United States},
year = {2017},
month = {6}
}