Transverse Photon Spectrum from QGP Fluid

We calculate the thermal photon distribution from the hot QCD matter produced by high energy nuclear collisions based on a hydrodynamical model, and compare it with the recent experimental data obtained by CERN WA80. Through the asymptotic value of the slo

TWC-97-1

TransversePhotonSpectrumfromQGPFluid

TetsufumiHirano,ShinMuroya ,andMikioNamiki

arXiv:nucl-th/9704010v2 8 Apr 1997

DepartmentofPhysics,WasedaUniversity,Tokyo169

TokuyamaWomen’sCollege,Tokuyama,Yamaguchi754

Abstract

WecalculatethethermalphotondistributionfromthehotQCDmatterpro-ducedbyhighenergynuclearcollisionsbasedonahydrodynamicalmodel,andcompareitwiththerecentexperimentaldataobtainedbyCERNWA80.Throughtheasymptoticvalueoftheslopeparameterofthetransversemomentumdistribu-tion,weinvestigatethecharacteristictemperatureoftheQCD uid.

Introduction

Sincethethermalphotonisconsideredtokeeptheinformationabouttheearlystageofthehotmatterproducedbyrelativisticnuclearcollisions,manytheoreticalanalyseshavealreadybeendone.ManygroupshaveanalyzedtheexperimentaldataofCERNWA80S+Au200GeV/nucleon[7]soasto ttheirtheoreticalmodeltothethermalphotonemissiondata.

InthispaperweanalyzethephotonandthehadrondistributionproducedbythehotQCDmatterinaconsistentway1.We rstchooseparametersinthehydrodynamicalmodelsoastoreproducethehadronicspectrum,i.e.,the(pseudo-)rapiditydistributionandthetransversemo-mentumdistribution.2.Wederivethethermalproductionrateofphotonsfromaunitspace-timevolumebasedonthe nitetemperature eldtheory.3.Accumulatingthethermalproductionrate,overthewholespace-timeregioncoveredwiththeparticlesource,whichisestimatedbythehydrodynamicalmodel,weeval-uatethethermalphotondistributionwhichistobecomparedwiththeexperimentaldata.

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