Enhanced Production of Direct Photons in Au+Au Collisions at {radical}(s{sub NN})=200 GeV and Implications for the Initial Temperature

Journal Article · Fri Apr 02 04:00:00 EDT 2010 · Physical Review Letters

DOI:https://doi.org/10.1103/PHYSREVLETT.104.132301· OSTI ID:21410610

Adare, A; Bickley, A A; Ellinghaus, F; Kelly, S; Kinney, E; Nagle, J L; Seele, J; Wysocki, M ^[1]; Afanasiev, S; Isupov, A; Litvinenko, A; Malakhov, A; Peresedov, V; Rukoyatkin, P; Zolin, L ^[2]; Aidala, C; Bjorndal, M T; Chi, C Y; Cole, B A; D'Enterria, D ^[3]

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1. University of Colorado, Boulder, Colorado 80309 (United States)
2. Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation)
3. Columbia University, New York, New York 10027 and Nevis Laboratories, Irvington, New York 10533 (United States)

The production of e{sup +}e{sup -} pairs for m{sub e}{sup +}{sub 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.

• OSTI ID: 21410610
• Journal Information: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 13 Vol. 104; ISSN 0031-9007; ISSN PRLTAO
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
ATOM COLLISIONS
ATOM-ATOM COLLISIONS
BOSONS
COLLISIONS
CONVERSION
DECAY
ELECTRONS
ELEMENTARY PARTICLES
ELEMENTS
ENERGY RANGE
FERMIONS
FIELD THEORIES
GEV RANGE
GOLD
HADRONS
INTERACTIONS
INTERNAL CONVERSION
LEPTONS
LINEAR MOMENTUM
MASSLESS PARTICLES
MATTER
METALS
MEV RANGE
NUCLEAR DECAY
PAIR PRODUCTION
PARTICLE INTERACTIONS
PARTICLE PRODUCTION
PHASE TRANSFORMATIONS
PHOTONS
PLASMA
POSITRONS
QUANTUM CHROMODYNAMICS
QUANTUM FIELD THEORY
QUARK MATTER
QUARK-GLUON INTERACTIONS
TRANSITION ELEMENTS
TRANSVERSE MOMENTUM