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1、三膠子以及三夸克彈性散射 與早期熱平衡化Xiao-MingXu,Y.Sun,A.-Q.Chen,L.Zheng,Nucl.Phys.A744(2004)347Gluonnumberdensityatτ=0.2fm/c:~38fm-3atRHIC~140fm-3atLHCAtveryhighgluonnumberdensity,three-gluonscatterings,four-gluonscatterings,five-gluonscatteringsetc.areimportant.Thiscanb
2、eshownbyMonteCarlosimulationsofinitialgluondistributionRA=6.4fm,Y=5,tini=0.2fm/cIftheclosestdistanceoftwogluonsislessthanagiveninteractionrange,ascatteringofthetwogluonsoccurs.Ifthreegluonsarewithinaspherewhichcenterisatthecenterofmassofthethreegluonsandw
3、hichradiusequalsthegiveninteractionrange,ascatteringofthethreegluonsoccurs.Ratioofthree-gluontotwo-gluonsecondaryscatteringnumbersversustheinteractionrangeEffectoftriple-gluonelasticscatterings:EarlythermalizationofgluonmatterinitiallyproducedincentralAu-
4、Aucollisions.Earlythermalization:athermalstateisachievedwithinatimeoflessthan1fm/cfromthemomentwhenquark-gluonmatterisinitiallycreatedinaAu-Aucollision.EarlyThermalizationEvidences:(1)Hydrodynamiccalculationsfortheellipticflowcoefficientv2haveshownthatmat
5、tercreatedinAu-Aucollisionsthermalizeswithinatimeoflessthan1fm/c.DuringthermalizationenergydensityiswellabovethecriticalvalueforQCDphasetransition.(2)Jetquenching(3)Two-jetcorrelationPhysics:triple-gluonelasticscatteringsleadtoearlythermalization.Thermali
6、zationbytwo-bodyelasticscatteringsisconventional:akilogramofcoldwater+akilogramofhotwater→twokilogramsofwarmwaterInthemixingprocess,theelasticscatteringsbetweenwatermoleculesestablishanewtemperature.Thermalizationbythree-bodyelasticscatteringsisnew.STARCo
7、llaboration,Phys.Rev.Lett.86(2001)402;90(2003)032301Scatteringsofthreegluons…….θ=0o–––θ=45o—-—θ=90o···θ=0o–––θ=45o–·–θ=90oTriple-quarkelasticscatteringsBoltzmann-typetransportequationforup-quarkdistributionfunctionThermalizationtimeofinitialquarkmatteris1
8、.8fm/c.Conclusions(1)Thethree-gluonscatteringprocessesgiveavariationofthegluondistributionfunctionconsiderablylargerthanthetwo-gluonscatteringprocesses.Thetriple-gluonelasticscatteringsdominatetheevolutionofgluonmat
