Photon and Neutral π⁰197Au + ¹⁹⁷Au collisions at √s_NN = 130 GeV

Thesis/Dissertation · Sun Sep 01 00:00:00 EDT 2002

DOI:https://doi.org/10.2172/806124· OSTI ID:806124

Johnson, Ian Jeffrey ^[1]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

Inclusive transverse momentum spectra of photons and π⁰s at mid-rapidity are studied as a function of collision centrality for ¹⁹⁷Au+ ¹⁹⁷Au collisions at √s_NN = 130 GeV. Photon pair conversions have been reconstructed from charged tracks measured by the main Time Project Chamber of the STAR experiment at the RHIC heavy ion facility. The transverse momentum resolution of photons with this method is estimated to be Δp_t/p_t = 2% at 0.125 GeV/c and 5% at 2.5 GeV/c. Photon spectra were measured up to a transverse momentum of 2.4 GeV/c between ± 0.5 units of rapidity. The dominant photon production mechanism, the π⁰ → γγ decay, was measured between 0.25-2.5 GeV/c and ± 1 units of rapidity. Spectra are reported for the top 11%, 11-34% and 34-85% centrality classes. It was observed that in mid-central and central collisions the relative contribution of the π⁰ → γγ decay to the inclusive photon spectrum decreases above a transverse momentum of 1.65 GeV/c. In central collisions the magnitude of the decrease from p_t = 1.65 GeV/c to 2.4 GeV/c is 20%. It is unlikely that contributions from other π⁰ decay channels and other particle decays fully explain this decrease. The centrality dependence on the shapes of the π⁰ spectra was analyzed with Boltmann and Bose-Einstein functions. In the transverse momentum windows of the spectra, the extracted temperatures are near 0.295 GeV. These temperatures are substantially higher than those extracted from π^± spectra in a lower range of transverse momentum. This is an indication that the shapes of the pion spectra deviate from purely exponential shapes.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 806124
• Report Number(s): LBNL-51506; R&D Project: NRNC; B& R KB0201022; TRN: US0301151
• Resource Relation: Other Information: TH: Thesis (Ph.D.); Submitted to the University of California, Davis, CA 95616 (US); PBD: 16 Sep 2002
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
74 ATOMIC AND MOLECULAR PHYSICS
DECAY
HEAVY IONS
INTERNAL PAIR PRODUCTION
PARTICLE DECAY
PHOTONS
PIONS
PRODUCTION
RESOLUTION
SPECTRA
TRANSVERSE MOMENTUM
WINDOWS
DIRECT PHOTONS PHOTON NEUTRAL PION STAR RHIC PAIR CONVERSION