Re-analysisof-中国科学院高能物理研究所.ppt

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1、ObservationofthresholdenhancementfromJiXiaobinIHEPOct.28–Nov.1,2006Phys.Rev.Lett.91,022001(2003)ContentIntroductionEventsSelectionResultsandDiscussionSummary晨光杯（桂林）L~~51030/cm2satJ/peakEcm~2-5GeVTheBeijingElectronPositronCollider晨光杯（桂林）VC:xy=100mTOF:T=180p

2、scounter:r=3cmMDC:xy=220mBSC:E/E=22%z=5.5cmdE/dx=8.5%=7.9mrBfield:0.4Tp/p=1.78%(1+p2)z=3.1cmBESIIDetector晨光杯（桂林）WorldJ/Samples(106)LargestfromBES晨光杯（桂林）EventsSelection2goodchargedtracks1(isolatedfromchargedtracks)ParticleIDforbothchargedtracks4C-

3、fitTheAnalysisof晨光杯（桂林）massfromselectedeventsBesidesCpeak,thereisaclearenhancementnearthreshold.晨光杯（桂林）BackgroundsMainbackgroundsremainedafterselectionformasspeaknearthresholdNoclearenhancementnearthreshold晨光杯（桂林）FitSignalwithanS(P)-waveBWq=daughtermomentumq0=da

4、ughtermomentum@peak晨光杯（桂林）FitresultsM(pp)-2mp(GeV)00.10.20.3c2/dof=56/56fittedpeaklocationM=1859MeV/c2G<30MeV/c2(90%CL)+3+5-10-25晨光杯（桂林）thresholdobservedpeakBW“peak”HighStatisticsiscrucialtothedeterminationofBW“peak”belowThreshold.MassDetermination晨光杯（桂林）Noturnov

5、eratthresholdpeakmassmustbe<2mpweighteventsbyq0/q:(i.e.removethresholdphasespacefactor)M(pp)-2mp(GeV)IsMpeakreallessthan2mp?晨光杯（桂林）P-wavefit??M=1876.4±0.9MeVG=4.6±1.8MeVc2/dof=59/56OK!M=2mp晨光杯（桂林）cosqgdistribution1+cos2qg(expectedforJ/yg0-+)sin2qgM(pp)<1.9GeV晨光

6、杯（桂林）FurtherChecksOnlyselectedeventswithPp>0.4GeV/c2PID:dE/dxTOF+dE/dx晨光杯（桂林）efficiencyOthertests(p>0.4)M=18592MeV=019MeVrecdEdx晨光杯（桂林）Othertests(PID)P(GeV/c)TOFP(GeV/c)PHMPdE/dxTOF+dE/dx晨光杯（桂林）Othertests(PIDdE/dxTOF+dE/dx)M=18562MeV=022MeV晨光杯（桂林）Ther

7、esultsarecompatiblewithpublishonesFurtherChecks晨光杯（桂林）PossibleunderstandingsofthenewobservationExcludeinterpretationsofknownresonances—Coulditbeatailofaknownresonance?—FSI(FinalStatesInteraction)?Baryoniuminterpretation晨光杯（桂林）Coulditbeatailofaknownresonance?0-+re

8、sonancesinPDGtables:h(1760)M=1760G=60MeVp(1800)M=1801G=210MeVDefinitelyexcluded!(>>5)2/dof=323/58c2/dof=412/58晨光杯（桂林）PureFSIdisfavoredI=0S-waveFSICANNOTfitth