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Title: Enhanced Production of Direct Photons in Au + Au Collisions at root SNN = 200 GeV and Implications for the Initial Temperature

Abstract

The production of e{sup +}e{sup -} pairs for m{sub e{sup +}e{sup -}} < 0.3 GeV/c{sup 2} and 1 < p{sub T} < 5 GeV/c is measured in p+p and Au+Au collisions at {radical}s{sub NN} = 200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of the direct photon yield over p+p is exponential in transverse momentum, with an inverse slope T = 221 {+-} 19{sup stat} {+-} 19{sup syst} MeV. Hydrodynamical models with initial temperatures ranging from T{sub init} {approx} 300-600 MeV at times of {approx} 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at {approx} 170 MeV.

Authors:
;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider
Sponsoring Org.:
USDOE SC OFFICE OF SCIENCE (SC)
OSTI Identifier:
1040383
Report Number(s):
BNL-91231-2010-JA
Journal ID: ISSN 0031-9007; PRLTAO; R&D Project: PO 003; KB0201021; TRN: US1202417
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Physical Review Letters
Additional Journal Information:
Journal Volume: 104; Journal Issue: 13; Journal ID: ISSN 0031-9007
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; INTERNAL CONVERSION; PHOTONS; PRODUCTION; QUANTUM CHROMODYNAMICS; QUARK MATTER; TRANSVERSE MOMENTUM; relativistic heavy ion collider

Citation Formats

Adare, A.d., and PHENIX Collaboration. Enhanced Production of Direct Photons in Au + Au Collisions at root SNN = 200 GeV and Implications for the Initial Temperature. United States: N. p., 2010. Web. doi:10.1103/PhysRevLett.104.132301.
Adare, A.d., & PHENIX Collaboration. Enhanced Production of Direct Photons in Au + Au Collisions at root SNN = 200 GeV and Implications for the Initial Temperature. United States. doi:10.1103/PhysRevLett.104.132301.
Adare, A.d., and PHENIX Collaboration. Fri . "Enhanced Production of Direct Photons in Au + Au Collisions at root SNN = 200 GeV and Implications for the Initial Temperature". United States. doi:10.1103/PhysRevLett.104.132301.
@article{osti_1040383,
title = {Enhanced Production of Direct Photons in Au + Au Collisions at root SNN = 200 GeV and Implications for the Initial Temperature},
author = {Adare, A.d. and PHENIX Collaboration},
abstractNote = {The production of e{sup +}e{sup -} pairs for m{sub e{sup +}e{sup -}} < 0.3 GeV/c{sup 2} and 1 < p{sub T} < 5 GeV/c is measured in p+p and Au+Au collisions at {radical}s{sub NN} = 200 GeV. An enhanced yield above hadronic sources is observed. Treating the excess as photon internal conversions, the invariant yield of direct photons is deduced. In central Au+Au collisions, the excess of the direct photon yield over p+p is exponential in transverse momentum, with an inverse slope T = 221 {+-} 19{sup stat} {+-} 19{sup syst} MeV. Hydrodynamical models with initial temperatures ranging from T{sub init} {approx} 300-600 MeV at times of {approx} 0.6-0.15 fm/c after the collision are in qualitative agreement with the data. Lattice QCD predicts a phase transition to quark gluon plasma at {approx} 170 MeV.},
doi = {10.1103/PhysRevLett.104.132301},
journal = {Physical Review Letters},
issn = {0031-9007},
number = 13,
volume = 104,
place = {United States},
year = {2010},
month = {4}
}