JPC8x44x518501102321q qcontent2S1LJ1LevenJ1LoddJ3LevenJ3LoddJ u du ud dd uI1 ID: 99540
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8.Namingschemeforhadrons8.NAMINGSCHEMEFORHADRONSRevised2004byM.Roos(UniversityofFinland)andC.G.Wohl(LBNL).8.1.IntroductionWeintroducedinthe1986edition[1]anewnamingschemeforthehadrons.Changesfromolderterminologya®ectedmainlytheheaviermesonsmadeofthelight(u;d;ands)quarks.Oldandnewnameswerelistedalongsideuntil1994.Namesalsochangefromeditiontoeditionbecausesomecharacteristiclikemassorspinchanges.TheSummaryTablesgiveboththenewandoldnameswheneverachangeoccurred.8.2.\Neutral-°avor"mesons(S=C=B=T=0)Table8.1showsthenamesformesonshavingthestrangenessandallheavy-°avorquantumnumbersequaltozero.Theschemeisdesignedforallordinarynon-exoticmesons,butitwillworkformanyexotictypestoo,ifneeded.Table8.1:Symbolsformesonswiththestrangenessandallheavy-°avorquantumnumbersequaltozero. JPC=8�&#x-4.4;å :0+1+10++2+3+21++............q qcontent2S+1LJ=1(Leven)J1(Lodd)J3(Leven)J3(Lodd)J u d;u ud d;d u(I=1)¼b½ad d+u uand/ors s(I=0)´;´0h;h0!;Áf;f0c c´chcycb b´bhbbt t´thtµÂt yTheJ=ÃremainstheJ=Ã.First,weassignnamestothosestateswithquantumnumberscompatiblewithbeingq qstates.TherowsoftheTablegivethepossibleq qcontent.Thecolumnsgivethepossibleparity/charge-conjugationstates,PC=+,+,,and++;thesecombinationscorrespondone-to-onewiththeangular-momentumstate2S+1LJoftheq qsystembeing1(Leven)J,1(Lodd)J,3(Leven)J,or3(Lodd)J:HereS,L,andJarethespin,orbital,andtotalangularmomentaoftheq qsystem.ThequantumnumbersarerelatedbyP=(1)L+1,C=(1)L+S,andGparity=(1)L+S+I;whereofcoursetheCquantumnumberisonlyrelevanttoneutralmesons.K.A.Oliveetal.(PDG),Chin.Phys.C38,090001(2014)(http://pdg.lbl.gov)August21,201413:18 8.NamingschemeforhadronsTheentriesintheTablegivethemesonnames.ThespinJisaddedasasubscriptexceptforpseudoscalarandvectormesons,andthemassisaddedinparenthesesformesonsthatdecaystrongly.However,forthelightestmesonresonances,weomitthemass.Measurementsofthemass,quarkcontent(whererelevant),andquantumnumbersI,J,P,andC(orG)ofamesonthus¯xitssymbol.Conversely,thesepropertiesmaybeinferredunambiguouslyfromthesymbol.Ifthemainsymbolcannotbeassignedbecausethequantumnumbersareunknown,Xisused.Sometimesitisnotknownwhetheramesonismainlytheisospin-0mixofu uandd dorismainlys s.Aprime(orpair!,)maybeusedtodistinguishtwosuchmixingstates.Wefollowcustomandusespectroscopicnamessuchas¨(1S)astheprimarynameformostofthose,¨,andstateswhosespectroscopicidentityisknown.Weusetheform¨(9460)asanalternative,andastheprimarynamewhenthespectroscopicidentityisnotknown.Namesareassignedfort tmesons,althoughthetopquarkisevidentlysoheavythatitisexpectedtodecaytoorapidlyforboundstatestoform.Gluoniumstatesorothermesonsthatarenotq qstatesare,ifthequantumnumbersarenotexotic,tobenamedjustasaretheq qmesons.Suchstateswillprobablybedi±culttodistinguishfromq qstatesandwilllikelymixwiththem,andwemakenoattempttodistinguishthose\mostlygluonium"fromthose\mostlyq q."An\exotic"mesonwithJPCquantumnumbersthataq qsystemcannothave,namelyJPC=0;0+;1+;2+;3+;¢¢¢;wouldusethesamesymbolasdoesanordinarymesonwithallthesamequantumnumbersastheexoticmesonexceptfortheCparity.ButthentheJsubscriptmaystilldistinguishit;forexample,anisospin-01+mesoncouldbedenoted!1.8.3.MesonswithnonzeroS,C,B,and/orTSincethestrangenessoraheavy°avorofthesemesonsisnonzero,noneofthemareeigenstatesofchargeconjugation,andineachofthemoneofthequarksisheavierthantheother.Therulesare:1.Themainsymbolisanupper-caseitalicletterindicatingtheheavierquarkasfollows:s! Kc!Db! Bt!T:Weusetheconventionthatthe°avorandthechargeofaquarkhavethesamesign.Thusthestrangenessofthesquarkisnegative,thecharmofthecquarkispositive,andthebottomofthebquarkisnegative.Inaddition,I3oftheuanddquarksarepositiveandnegative,respectively.Thee®ectofthisconventionisasfollows:Any°avorcarriedbyachargedmesonhasthesamesignasitscharge.ThustheK+,D+,andB+havepositivestrangeness,charm,andbottom,respectively,andallhaveAugust21,201413:18 8.NamingschemeforhadronspositiveI3.TheD+shaspositivecharmandstrangeness.Furthermore,the¢(°avor)=¢Qrule,bestknownforthekaons,appliestoevery°avor.2.Ifthelighterquarkisnotauoradquark,itsidentityisgivenbyasubscript.TheD+sisanexample.3.Ifthespin-parityisinthe\normal"series,JP=0+;1;2+;¢¢¢,asuperscript\"isadded.4.Thespinisaddedasasubscriptexceptforpseudoscalarorvectormesons.8.4.Ordinary(3-quark)baryonsThesymbolsN,¢,¤,§,¥,andusedformorethan30yearsforthebaryonsmadeoflightquarks(u,d,andsquarks)telltheisospinandquarkcontent,andthesameinformationisconveyedbythesymbolsusedforthebaryonscontainingoneormoreheavyquarks(candbquarks).Therulesare:1.Baryonswiththreeuand/ordquarksareN's(isospin1/2)or¢'s(isospin3/2).2.Baryonswithtwouand/ordquarksare¤'s(isospin0)or§'s(isospin1).Ifthethirdquarkisac,b,ortquark,itsidentityisgivenbyasubscript.3.Baryonswithoneuordquarkare¥'s(isospin1/2).Oneortwosubscriptsareusedifoneorbothoftheremainingquarksareheavy:thus¥c,¥cc,¥b,etc.4.Baryonswithnouordquarksare's(isospin0),andsubscriptsindicateanyheavy-quarkcontent.5.Abaryonthatdecaysstronglyhasitsmassaspartofitsname.Thusp,§,,+c,etc.,but¢(1232)0,§(1385),¥c(2645)+,etc.Inshort,thenumberofuplusdquarkstogetherwiththeisospindeterminethemainsymbol,andsubscriptsindicateanycontentofheavyquarks.A§alwayshasisospin1,analwayshasisospin0,etc.8.5.ExoticbaryonsIn2003,severalexperimentsreported¯ndingastrangenessS=+1,chargeQ=+1baryon,andoneexperimentreported¯ndinganS=2,Q=2baryon.Baryonswithsuchquantumnumberscannotbemadefromthreequarks,andthustheyareexotic.TheS=+1baryon,whichoncewouldhavebeencalledaZ,wasquicklydubbedthe£(1540)+,andweproposedtonametheS=2baryonthe©(1860).However,these\discoveries"werethencompletelyruledoutbymanyexperimentswithfarlargerstatistics:Seeour2008Review[2].August21,201413:18 8.NamingschemeforhadronsFootnoteandReference:Sometimesaprimeisnecessarytodistinguishtwo¥c'sinthesameSU(n)multiplet.Seethe\NoteonCharmedBaryons"intheCharmedBaryonListings.1.ParticleDataGroup:M.Aguilar-Benitezetal.,Phys.Lett.170B(1986).2.ParticleDataGroup:C.Amsleretal.,Phys.Lett.B667,1(2008).August21,201413:18