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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