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《Measurement of Sivers Asymmetries for Di-jets in sqrt{s}=200 GeV pp Collisions at STAR》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、MeasurementofSiversAsymmetriesforDi-jets√ins=200GeVppCollisionsatSTARJ.BalewskifortheSTARCollaborationIndianaUniversityCyclotronFacility,2401MiloB.SampsonLane,Bloomington,IN,47408Abstract.Measurementofthetransversespindependenceofthedi-jetopeningangleinppcol-√lisionsats=200GeVhasbeenperformedb
2、ytheSTARcollaboration.Ananalyzingpowerconsistentwithzerohasbeenobservedoverabroadrangeinpseudorapiditysumofthetwojetswithrespecttothepolarizedbeamdirection.Anon-zero(Sivers)correlationbetweentransversemomentumdirectionofpartonsintheinitialstateandtransversespinorientationoftheparentpro-tonhasb
3、eenpreviouslyobservedinsemi-inclusivedeepinelasticscattering(SIDIS).ThepresentmeasurementsaremuchsmallerthandeducedfrompredictionsmadeforSTARdi-jetsbasedonnon-zeroquarkSiversfunctionsdeducedfromSIDIS,andfurthermoreindicatethatgluonSiversasymmetriesarecomparablysmall.Keywords:ppcollisions,RHIC,
4、STAR,di-jet,transversepolarization,singlespinasymmetry,Siversfunctions,An,pseudorapidity-dependencePACS:12.39,13.87,13.88,24.85Experimentaldeterminationofthecontributionfromorbitalangularmomentumoftheproton'sconstituentstoitsspinisdifficult.ApossiblemanifestationoforbitalmomentumareSiverscorrel
5、ations[1]betweenthetransversespin(S~T)directionofapolarizedprotonandtransversemomentum(k~⊥)directionalpreferencesofunpolarizedpartonscarryinglongitudinalmomentumfractionxoftheproton:~P·k~⊥×S~T1N⊥Df(x,k)(1)2
6、~P
7、·
8、k~⊥
9、·
10、S~T
11、arXiv:hep-ex/0612036v114Dec2006where~Pisthemomentumvectorofthepolarize
12、dprotonandDNf(x,k⊥)iscalledtheSiversfunction.Recentlymeasurementofanon-zeroSiversfunctionforp+inSIDIShasbeenreportedbytheHERMEScollaboration[2].Thesamegroupfoundanasymmetryconsistentwithzeroforp−,leadingtoaninterpretation[3]thattheSiversfunctionsareoppositeinsignanddifferentinmagnitudeforuvs.d
13、quarks.BoerandVogelsang[4]suggestedthattheSiverseffectwouldbemanifestedasaspin-dependentazimuthalsidepreferenceforalmostback-to-backdi-jetsproducedinprotoncollisionsinvolvingtransverselypolarizedbeam.InthispaperwereportSiverssinglespina
