Hadron Spectroscopy with COMPASS -- Newest Results

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1、HadronSpectroscopywithCOMPASS–NewestResultsFrankNerlinga,fortheCOMPASScollaborationPhysikalischesInstitut,Albert-Ludwigs-UniversitatFreiburg¨/CERNPHDepartment,GenevaAbstract.TheCOMPASSexperimentattheCERNSPSinvestigatesthestructureandspectrumofhadronsbyscatterin

2、ghighenergetichadronsandpolarisedmuonsovariousfixedtargets.Duringtheyears2002-2007,COMPASSfocusedonnucleonspinphysicsusing160GeV/cpolarised+beamsonpolariseddeuteronandprotontargets,includingmeasurementsofthegluoncontributiontothenucleonspinusinglongitudinaltarg

3、etpo-larisationaswellasstudiesoftransversespineectsinthenucleononatransverselypo-larisedtarget.Onemajorgoalofthephysicsprogrammeusinghadronbeamsisthesearchfornewstates,inparticularthesearchforJPCexoticstatesandglue-balls.COMPASSmeasuresnotonlychargedbutalsoneut

4、ralfinal-stateparticles,allowingforinvestigationofnewobjectsindierentreactionsanddecaychannels.InadditionCOMPASScanmea-surelow-energyQCDconstantslike,e.g.theelectromagneticpolarisabilityofthepion.Apartfromafewdayspilotrundatatakenin2004witha190GeV/cbeamonaPbta

5、r-get,showingasignificantspin-exoticJPC=1+resonanceataround1660MeV/c2,COM-PASScollectedhighstatisticswithnegativeandpositive190GeV/chadronbeamsonaproton(H2)andnuclear(Ni,Pb)targetsin2008and2009.Wegiveaselectedoverviewofthenewestresultsanddiscussthestatusofvario

6、usongoinganalyses.1IntroductionTheCOMPASSfixed-targetexperimentisafacilitytostudyQCD,coveringalargerangeinmomen-tumtransferfromlargerthan1GeV2/c2downtosmallerthan103GeV2/c2.Physicstopicsaddressedisthestudyofhadronstructureanddynamics,comprisingtheinvestigationo

7、fnucleonspin-structureusingapolarisedmuonbeam,seee.g.[1]forarecentsummary,andhadronspectroscopyusinghadronbeamstostudythemassspectrumofhadrons,totestChiralPerturbationTheory(ChPT)andtomea-surethefundamentalquantitiesofpionandkaonpolarisibilities.Oneimportantgoa

8、lofthephysicsprogrammeusinghadronbeamsisthesearchfornewstates,likespin-exoticmesonsandglue-balls.SuchstatesarebeyondthesimpleConstituentQuarkModel(CQM),however,theyareallowe