北京谱仪上光子转换过程的重建与光子能量的精确测量

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1、130ò15ÏpUÔn†ØÔnVol.30,No.52006c5HIGHENERGYPHYSICSANDNUCLEARPHYSICSMay,2006ReconstructionofPhotonConversionsandPreciseMeasurementofPhotonEnergyatBES/*1;2;1)31ZHANGChang-ChunWANGZheYUANYe1(InstituteofHighEnergyPhysics,CAS,Beijing100049,China)2(DepartmentofTechnicalPhysi

2、cs,PekingUniversity,Beijing100871,China)3(DepartmentofEngineeringPhysics,TsinghuaUniversity,Beijing100084,China)AbstractUsingMonteCarlosimulation,reconstructionofphotonconversionsisstudied,andthedetectioneciencyandenergyresolutionasafunctionofphotonenergyareobtained.T

3、hedE=dxcorrectionfortheelectronsfromphotonconversionsandtheenergyscaleforthephotonsarecalibratedwithBES/data.AnimprovedCrystalBallfunctiondescribeswelltheenergydistributionofthephotons.Photonenergyresolutionsintherangefrom2.3to3.8MeVarefoundforthephotonswithenergyfrom1

4、00to260MeVattheBES/detector.Keywordsphotonconversion,photonreconstruction,dE=dxcorrection,photonenergyresolution,BES/detector1Introduction260MeVusingGEANT3basedMonteCarlo(MC)[3]simulationpackageSIMBES.MCstudyshowsthatPrecisemeasurementofphotonenergy,speciallymomentumre

5、solutionfrom1.6to4.1MeV/cintheforlowenergyphotons,isanimportantissueinhighcentralpartofthemomentumdistributioncanbeob-energyphysicsexperiments.Photonsproducedinthetainedforelectronscarryingmomentumaslowas60J=! c(1S)and(2S)! cJ(J=0;1;2)ra-to250MeV/c,butatailappearsatt

6、helowersideofdiativedecayscarryanenergyfrom115to261MeV.thedistribution.Theelectronsproducedfromcon-TheCsI(Tl)crystalcalorimeteratCLEOprovidesversionprocessofphotonswithenergyfrom100toanenergyresolutionof4.8MeVfor100MeVenergy260MeVoccurjustinthislowmomentumregion.[1]pho

7、ton.However,energyresolutioninacalorime-Momentumcorrectionduetoionizationenergylossterconsistingofproportionalwirechamberorself-(dE=dx)fortheelectronsandenergyscaleforthequenchingstreamertubesismuchworse.Itisin-photonsarecalibratedusingtheJ=and(2S)data,terestingtoexplo

8、reanewmethodforphotonenergycollectedbytheBES/detectoroperatingatthe+measurementwithanimprovedenergyresolutionatBEPCe