Search for Disoriented Chiral Condensates in 158 AGeV Pb+Pb(9)

The restoration of chiral symmetry and its subsequent breaking through a phase transition has been predicted to create regions of Disoriented Chiral Condensates (DCC). This phenomenon has been predicted to cause anomalous fluctuations in the relative produ

Weverifythebinomialnatureofthecharge uctuationsinVENUSbystudy-ingits“binomiality”:

B=Nπch pchNπ(3)pch(1 pch)Nπ

whereNπchandNπarenumberofchargedpionsandthetotalnumberofpionsforeachevent,andpch=Nπch/Nπistheprobabilitythatapionischarged.Forapurebinomialdistribution,pch=2/3andBisGaussianwithameanatzeroandanRMSofone.ForVENUSwithoutGEANT,we ndanRMSofapproximately.95forpionsproducedinthecentralrapidityregionineventswithanimpactparameterlessthan6fm.ThisisconsistentwiththehypothesisthatthecorrelationarisesmainlyfromthebinomialpartitionofNπ,thetotalpionmultiplicity.

4Event-by-EventSearchforDCCs

DCCsshouldmodifythebinomialpartitioningofNπintochargedandneutralpions.EventsinwhichaDCCisproduced(henceforthreferredtoas“DCCevents”)willshowupasdeviationsfromthebinomialbehaviorandappearasoutlierswithrespecttothebulkofthedata.Wehavealreadydiscussedthatthechargedandneutralmultiplicitiesaredirectlysensitivetothechargedandneutralpionmultiplicitiesineachevent.Thus,DCCeventsshouldappearinthecorrelationofchargedandneutralmultiplicities,whiletheindividualdistributionswillbemainlyuna ected.

4.1DataAnalysis

Thestrongcorrelationbetweenchargedandneutralmultiplicitiesdescribedabovesuggestsamoreappropriatecoordinatesystemwithoneaxisbeingthemeasuredcorrelationaxisandtheotherperpendiculartoit.Ifalldetectedparticleswerepionsandthedetectorswereperfectandhadidenticalpseudo-rapidityacceptance,thenthecorrelationaxiswouldbeastraightline.Instead,wemustaccountforthefactthatathighmultiplicities,thepseudorapiditydistributionstendtonarrow,changingtherelativeacceptanceofchargedandneutralparticlesduetothenon-identicalaperturesoftheSPMDandPMD.Moreover,thelargeoccupanciesinthePMDleadtoaslightsaturatione ect.Itisthenusefultode neacoordinatesystemconsistingofacorrelationaxis(Z)describedbyasecond-orderpolynomial,andtheperpendiculardistance(DZ)fromit,whichisde nedtobepositiveforpointsbelowthisZaxis.