Relativistic isobar^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zrcollisions have revealed intricate differences in their nuclear size and shape,inspiring unconventional studies of nuclear structure using relativistic heavy ion collisions.In this study,we investigate the relative differences in the mean multiplicityR_()and the secondR_(ε2)and third-order eccentricityR_(ε3)between isobar collisions using initial state Glauber models.It is found that initial fluctuations and nuclear deformations have negligible effects on R_()in most central collisions,while both are important for the R_(ε2)and R_(ε3),the degree of which is sensitive to the underlying nucleonic or sub-nucleonic degree of freedom.These features,compared to real data,may probe the particle production mechanism and the physics underlying nuclear structure.
In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.
J.AdamL.AdamczykJ.R.AdamsJ.K.AdkinsG.AgakishievM.M.AggarwalZ.AhammedI.AlekseevD.M.AndersonA.AparinE.C.AschenauerM.U.AshrafF.G.AtetallaA.AttriG.S.AverichevV.BairathiK.BarishA.BeheraR.BellwiedA.BhasinJ.BielcikJ.BielcikovaL.C.BlandI.G.BordyuzhinJ.D.BrandenburgA.V.BrandinJ.ButterworthH.CainesM.Calderon de la Barca SanchezD.CebraI.ChakaberiaP.ChaloupkaB.K.ChanF-H.ChangZ.ChangN.Chankova-BunzarovaA.ChatterjeeD.ChenJ.ChenJ.H.ChenX.ChenZ.ChenJ.ChengM.CherneyM.ChevalierS.ChoudhuryW.ChristieX.ChuH.J.CrawfordM.CsanadM.DaugherityT.G.DedovichI.M.DeppnerA.A.DerevschikovL.DidenkoX.DongJ.L.DrachenbergJ.C.DunlopT.EdmondsN.ElseyJ.EngelageG.EppleyS.EsumiO.EvdokimovA.EwiglebenO.EyserR.FatemiS.FazioP.FedericJ.FedorisinC.J.FengY.FengP.FilipE.FinchY.FisyakA.FranciscoL.FulekC.A.GagliardiT.GalatyukF.GeurtsA.GibsonK.GopalX.GouD.GrosnickW.GurynA.I.HamadA.HamedS.HarabaszJ.W.HarrisS.HeW.HeX.H.HeY.HeS.HeppelmannS.HeppelmannN.HerrmannE.HoffmanL.HolubY.HongS.HorvatY.HuH.Z.HuangS.L.HuangT.HuangX.HuangT.J.HumanicP.HuoG.IgoD.IsenhowerW.W.JacobsC.JenaA.JentschY.JiJ.JiaK.JiangS.JowzaeeX.JuE.G.JuddS.KabanaM.L.KabirS.KagamasterD.KalinkinK.KangD.KapukchyanK.KauderH.W.KeD.KeaneA.KechechyanM.KelseyY.V.KhyzhniakD.P.KikołaC.KimB.KimelmanD.KincsesT.A.KinghornI.KiselA.KiselevM.KocanL.KochendaL.K.KosarzewskiL.KramarikP.KravtsovK.KruegerN.Kulathunga MudiyanselageL.KumarS.Kumar
We studied the chiral magnetic effect in AuAu,RuRu,and ZrZr collisions at sNN−√=200GeV.The axial charge evolution was modeled with stochastic hydrodynamics,and geometrical quantities were calculated with the Monte Carlo Glauber model.By adjusting the relaxation time of the magnetic field,we found our results are in good agreement with background subtracted data for AuAu collisions at the same energy.We also made predictions for RuRu and ZrZr collisions.We found a weak centrality dependence on initial chiral imbalance,which implies that the centrality dependence of chiral magnetic effect signals results mainly from the effects of the magnetic field and volume factor.Furthermore,our results show an unexpected dependence on system size.While the AuAu system has larger chiral imbalance and magnetic field,it was observed to have a smaller signal for the chiral magnetic effect due to the larger volume suppression factor.
