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1、第29卷第1期高能物理与核物理Vol.29,No.12005年1月HIGHENERGYPHYSICSANDNUCLEARPHYSICSJan.,2005*EffectsofthePionStringatHeavyIonCollisions1;1)1,2MAOHongLIYun2De1(InstituteofHighEnergyPhysics,CAS,Beijing100049,China)2(PhysicsDepartment,EastChinaNormalUniversityShanghai,Shanghai200062,China)AbstractWes
2、tudythepossiblesignalsofthepionstringassociatedwiththeQCDchiralphasetransitioninLHCPb2Pbcollisionatenergys=5.5TeV.WefollowtheKibble2Zurekmechanismtodiscusstheproductionandevolutionofthepionstring.WewillshowthatiftheQCDchiralphasetransitionreallytakesplaceintheLHCPb2Pbcollisionproce
3、ssandthephasetransitionisinthesecondorder,thepionstringwillbeinevitablyproducedandsubsequentlydecay.Themaineffectofthisphenomenonisthatthereisagenerationofalargenumberofpionsinthefinalstateproducedbythedecayofthepionstring,andthesepionsaremostlydis2tributedinalowmomentumregionwithp
4、~143MeV;alsotherearelotsofneutralpionsdistributedinalowmomentumregionwiththemeanmomentumatp~21MeV.KeywordsPstring,Kibble2Zurekmechanism,heavyioncollisionsSeveralyearsagoRef.[1]discoveredatypeofclassi2sions.InRef.[6]theeffectofthepionstringontheprimor2calsolution,thepionstring,inthe
5、linearsigmamodelofdialmagneticfieldgenerationintheearlyuniversehasbeenSU(2)L@SU(2)R~O(4)whichhadbeenstudiedwidelyinconsideredanditscosmologicalsignificanceispointedout.IntheliteratureforthedescriptionoftheQCDchiralsymmetrythispaperwestudyapossiblesignalofthepionstringinthebreaking.
6、Thispionstringisverymuchlikethespinvortexheavyioncollisionandshowanotherkindofthesignificanceproducedatthesuperfluidtransitionoftheliquid3He[2].Justofthepionstringinlaboratoryexperiments.liketheZstring[3]inthestandardelectroweakmodel,thepi2TheLagrangianoftheSU(2)L@SU(2)R~O(4)lin2ea
7、rsigmamodelisgivenbyonstringisnottopologicallystablesinceanyfieldconfigura222tioncanbecontinuouslydeformedtothetrivialvacuumintheL+L+fP5=Tr[(5L5)(55)]-KTr(55)-,(1)2QCDsigmamodel.Withfinitetemperatureplasma,however,0SS0Ref.[4]arguedthatthepionstringcanbestabilized.Theywhere5=R+iP#,S
8、istheunitymatrixandSisthe2
