Search for Disoriented Chiral Condensates in 158 AGeV Pb+Pb(11)

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

determineupperlimitsonthefrequencyofDCCproductionasafunctionofitssize,asrepresentedbyζ.

WehavecomputedSZdistributionsforseveralvaluesofζ,rangingfrom15%to90%.Tode neane ciencyfordetectingDCCs,westartfromtheobser-vationthatthedistributionassumingthenullhypothesisisGaussian.Withourstatistics,weexpectfeweventsfartherthan5to6σfromthemean.AneventcontainingaDCC,however,hasanenhancedprobabilityofbeingfoundinthisregion.Thecut|SZ|>Scutthende nesatwo-dimensionalregioninthescatterplotinwhichalleventsareconsideredtobe“DCCcandidates”.Oncethecutisset,theDCCe ciencyisde ned,forNMCVENUSevents,as

(Scut,ζ)=N(|SZ|>Scut,ζ)

NCentral(Scut,ζ)≤NU.L.

NData.(5)

Wehavecalculatedlimitsfortwoscenarios.The rstisbaseduponthecon-servativeassumptionthatVENUSshoulddescribethedataperfectlyintheabsenceofaDCCsignal.Undertheseassumptions,SZ=DZ/σDZasobtained

fromVENUS(asitwasinFigure5)andScut=6.,whichiswellawayfromthedatapointwiththelargestSZ.The90%C.L.limitispresentedinFigure6asasolidline.Theotherscenarioassumesthatthedi erencebetweenthedataandVENUSisduetodetectore ectsandthatthewidthsshouldbethesame.Inthiscase,SZ=DZ/σDZ,withσDZtakenfromthedata,andwe

chooseatightercutScut=5.Thislimitispresentedinthesame gureasadashedline.Thetwolimitsarequitedi erentatζ=15%butgetcloseratζ>30%.Inbothcases,theuncertaintyintheabsolutecomparisonsbetweenthedataandVENUShavenotbeenincludedintheupperlimitestimate.