Application of a Neural Network and a Genetic Algorithm in the Analysis of Multi Particle F

《Application of a Neural Network and a Genetic Algorithm in the Analysis of Multi Particle F》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、ApplicationofaNeuralNetworkandaGeneticAlgorithmintheAnalysisofMultiParticleFinalStatesThomasF.Degener,MarcelKunzeFakultätfürPhysikundAstronomie,LehrstuhlIfürExperimentalphysik,Ruhr-UniversitätBochum,Universitätsstr.150,44801Bochum,Germanye-mail:thomas@tau.ep1.ruhr-uni-bochum.

2、deABSTRACTTheanalysisofaparticlephysicsexperimentrequiresthecorrectselectionofthedesiredmultiplicityofcharged(pionsorkaons)andneutral(photons)particles.Duetofluctuationsinhadronicandelectromagneticshowersoftentoomanyphotonsarereconstructedbytheanalysissoftware.Thecombinationof

3、afeedforwardneuralnetworkandageneticalgorithmisusedtoseparatephotonsandfluctuations.1.IntroductionThenumberofchargedparticlesarisingfrompp-annihilationmeasuredbytheCrystalBarreldetector1atLEAR(CERN)isdeterminedbycountingthenumberoftracksinthewirechambersoftheexperiment.Thecurv

4、atureofthetracksinamagneticfieldof1.5TanddE/dxinformationprovidethecorrespondingfourvectors.ThemeasurementofphotonsisdonebyuseofasegmentedCsI(Tl)-calorimeter.Inordertodeterminethenumberofphotonsandtheirfourvectors,neighbouringcrystalswithanenergydepositaregroupedtoformclusters

5、.Theseclustersaresearchedforlocalmaximatoresolvephotonsofwhichtheelectromagneticshowersareoverlapping.Itisassumedthateverylocalmax-imumcorrespondstoaphoton,iftheenergydepositinthewholeclusterisaboveathresh-old.MonteCarlostudiesshowthatabout5%ofalllocalmaximaarejustduetofluctua

6、tionsintheelectromagneticcascade.Aneuralnetworkhasbeendevelopedthatreducestheseelectromagneticfluctuationstolessthan0.1%.Afulldescriptionofthehier-archicnetworkarchitectureisgivenintheproceedingsoftheIII.workshop2.Thesimulta-neousmeasurementofchargedandcalorimetersurfaceneutra

7、lparticlesmakestheanalysismorecomplicated,becausechargedparticlesdepositenergyinthecalorime-tertoo.Topreventthemisinterpretationtrackpointsofthesurplusenergy(minimumioniz-5˚¡energydepositingpeakof180MeV)inthecalorime-vertexterasphotons,alldepositsinaconeFig.1Matchingofcharged

8、trackstowithanopeningangleof5˚¡aroundtheenergydepositsinthecalorimet