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nism[4].InordertoclarifyfinallywhatistheunderlyingmechanismbehindtheobservedZc(3900)struc
tureandotherexoticstructures,moreexperimentalandtheoreticaleffortsarerequired.
Fig.1ThetypicaldiagramsdepictingY(4260)→犑/ψπ+π- decay.Here,(a)denotesY(4260)directdecay
into犑/ψπ+π-;(b)describestheintermediatehadronicloopcontributiontoY(4260)→犑/ψπ
+π-;(c)and
(d)arefromtheISPEmechanism.
Fig.2Thedistributionsofthe犑/ψπ+andπ
+π-invariantmassspectraofY(4260)→π
+π-犑/ψ.The
fullcirclesandtriangleswitherrorbarsaretheexperimentaldatagivenbyBESIII[1]andBelle
[5],respectively.TheredhistogramsareourresultsconsideringcontributionsoftheISPEmechanismtothe
Y(4260)→π+π-犑/ψdecay.
犚犲犳犲狉犲狀犮犲狊
[1]M.Ablikim,etal.,[BESIIICollaboration],Phys.Rev.Lett.,110(2013)252001.[2]D.Y.Chen,X.Liu,Phys.Rev.,D84(2011)034032.[3]D.Y.Chen,X.Liu,T.Matsuki,arXiv:1208.2411[hepph].[4]D.Y.Chen,X.Liu,T.Matsuki,Phys.Rev.,D88(2013)036008.[5]Z.Q.Liu,etal.,[BelleCollaboration],Phys.Rev.Lett.,110(2013)252002.
17 犘狉犲犱犻犮狋犻狅狀狊狅犳犆犺犪狉犵犲犱犆犺犪狉犿狅狀犻狌犿犾犻犽犲犛狋狉狌犮狋狌狉犲狊ChenDianyong
ThenewexperimentalobservationgivenbyBESIII[1]notonlybringsusexcitement,sincetheob
servedcharmoniumlikestructureZc(3900)isverysimilartoourpredictionsbytheInitialSinglePionEmission(ISPE)mechanism
[2],butalsofurtherstimulatesustothinkabouthowtoincorporatetheISPEmechanismwithotherphenomena,i.e.,itsapplicationtomoredecayprocessesandgivemoretheoreticalpredictions.Alongthisway,wenoticethatbothofpionandkaoncanbecategorizedaschiralparticles.Thus,hiddencharmdikaondecaysofahighercharmoniumaretheintriguingprocesses,wheretheInitialSingleChiralparticleEmission(ISChE)mechanismcanplayanimportantroleinthesedecays,whichisanaturalextensionoftheISPEmechanism.Tosomeextent,theISPEmechanismcanbeincludedintheISChEmechanism.
ApplyingtheISChEmechanismtotheprocessesofdikaondecayofhighercharmoniumorcharmoni
umlikestate,onerequirestworelations犿ψ犻 >犿犓 +犿犇 +犿犇狊and 犿ψ犻 >犿ψ犳 +犿犓+ +犿犓- ,which
providethecriteriatochoosesuitableprocesses.Theminimumofthesumofthemassesofkaon,犇(),
and犇()狊 isabout4331MeV.Thus,themassofaninitialhighercharmonium mustbehigherthan4331
11 2013 IMP& HIRFLAnnualReport
MeV,whenwestudythehiddencharmdikaondecaysofahighercharmoniumbytheISChEmechanism.Thus,inthisworkthehiddencharmdikaondecaysofhighercharmoniaorcharmoniumlikestatesinclude
Y(4660)→珡K[犇犛()珡犇
()]/K[珡犇犛()犇
()]→犑/ψK+K-,
ψ(4790)→珡K[犇犛()珡犇
()]/K[珡犇犛()犇
()]→犑/ψK+K-.
Fig.1Dependenceofthedistributionof犱Γ/犱犿犑/ψK+ onthe犑/ψK+invariantmassspectrum
[3].The
diagrams(a)and(d),diagrams(b)and(e),anddiagrams(c)and(f),aretheresultsconsideringthe
intermediate犇珡犇犛+H.C.,犇珡犇犛+犇珡犇犛+H.C.,and犇珡犇犛
+H.C.contributions,respectively.Here,thelineshapeofdistributionofdΓ/犱犿犑/ψK+ isnormalizedto1.
WepresentthelineshapeofthedikaondecayofY(4660)andψ(4790)resultedfromtheISChEmech
anisminFig.1.Theverticallinesindicatethethresholdsof犇()珡犇犛
().Ifconsideringtheintermediate犇
珡犇犛+犇珡犇犛+H.C.contributiontoY(4660)→犑/ψK
+K-,wenoticethatthereexisttwostructuresinthe
lineshapeshowninFig.1(b).Thehigheroneisasharppeakstructurenearthe犇犛珡犇/珡犇狊
犇thresholds,
whiletheloweroneisabroadstructureasareflectionofthehigherone.Ifonlyincludingtheintermediate
犇珡犇犛+H.C.,theresultantdistributionof犱Γ/犱犿犑/ψ犓+ ofY(4660)→犑/ψK
+K- givesasmallsharp
peakstructurearoundthe犇珡犇犛
threshold.Inaddition,itsreflectionraisedas3.7GeVisobscure(seeFig.1(c)formoredetails).Asfortheψ(4790)→犑/ψK
+K- decay,wepresentthecorrespondingline
shapesof犱Γ/犱犿犑/ψK+ distributionbyconsideringtheintermediates犇珡犇犛+犇珡犇
犛 +H.C.and犇
珡犇犛 +H.
C.contributionsindiagrams(e)and(f)ofFig.1.TheFig.1(e)showsanenhancementstructureexisting
inthe犱Γ/犱犿犑/ψK+ distribution,whichiscomposedofasharppeaknearthe犇犛珡犇/珡犇
狊犇thresholdandits
reflection.ThissituationisdifferentfromthatofY(4660)→犑/ψK+K-justmentionedabove.Fig.1(f)in
dicatesasharppeakstructureclosetothe犇珡犇
犛thresholdandabroadstructurecorrespondingtoitsre
flection,whicharemoreclearcomparedwiththestructuresshowninFig.1(c).
犚犲犳犲狉犲狀犮犲狊
[1]M.Ablikim,etal.,[BESIIICollaboration],Phys.Rev.Lett.,110(2013)252001.[2]D.Y.Chen,X.Liu,Phys.Rev.,D84(2011)034032.[3]D.Y.Chen,X.Liu,T.Matsuki,Phys.Rev.Lett.,110(2013)232001.
21 IMP& HIRFLAnnualReport 2013