·16·
IMP&HIRFLAnnualReport
2017
Aswecanseefromtheabovesolutions,theBPSskyrmionsolutionhasnobindingenergywhichtellsthatthesolutionisstableandsotheologyinBPSSkyrmemodelisalsostable.Moreover,onecanseeaclearstructureattheboundaryofsolutionn=
1.Checkingtheintegralenergyandbaryoncharge,wefindthattheboundaryindeedseparatesn=2solutionintotwoskyrmioinswithsameenergyandbayronchargeandthiscouldbeviewedasshellstructureinabaryon. References [1]
Y.M.Cho,KyoungtaeKimm,
J.H.Yoon,etal.,Eur.Phys.J.C,77(2017)88.[2]
T.H.R.Skyrme,Proc.Roy.Soc.(London),260(1961)127;262(1961)237;Nucl.Phys.,31(1962)556.[3]
C.Adam,S´anchez-Guill´enJ,
A.Wereszczyn´ski,Phys.Rev.D,82(2010)085015. ∗Foundationitem:NationalNaturalSciencefoundationofChina(11575254,11475227). 1-11GettingtheMostNeutrinosoutofIsoDAR∗
E.Ciuffoli,
H.Mohammed,
J.Evslin,
F.Y.ZhaoandM.Deliyergiyev SeveralexperimentsintendtouseneutrinosproducedviaeDecayAtRest(IsoDAR)tosearchforsignsofthepresenceofsterileneutrinos.InmostIsoDARexperimentsspallationneutronsareabsorbedina7Lisleeve(converter),creating8Li,thatwilldecayemittingν¯e.OftenIsoDARproposalsplantouseexistingdetectorsorelerators,toreducethecostoftheexperiment.Inparticular,ithasbeenproposedtouseasaneutronsourcethehigh-intensityprotoneleratorsthatwillbebuiltasapartoftheChinaeleratorDrivenSystem(C-ADS)program[1]. UsingGeant4andFLUKAsimulations,westudiedtheoptimizationofthetargetstation,focusinginparticularontheneutronyieldandonthe8Liproduction.Ifthetargetissurroundedbyaconverteroramoderator,theneutronscanbounceback.Thisisaproblemespeciallyinthecaseofheavymetaltargets,whichhavealargeneutronabsorptioncrosssection:inthecaseofW,upto40%oftheneutronscanbelostduetothebounceback.Wefoundoutthatthiseffectcanbereducebyplacingagap(vacuumsleeve)betweenthetargetandtheconverter.Forexample,witha20cmgaptheneutronlosscanbedecreaseddowntolessthan20%. Inordertobeabsorbedintheconverter,theneutronsmustbefirstsloweddowntothermalenergies.InthefirstIsoDARproposal,forthispurposeaheavywatersleeve(moderator)wasplacedbetweenthetargetandtheconverter;howeverinthiswayeithermostofneutronsarenotthermalizedorasignificantfractionofthemisabsorbedinsidethemoderator.Apossiblesolutionistomixthemoderatorwiththeconverter.Forexample,usinglithiumdeuteroxide(eitherinitsanhydrousform,LiOD,ormonohydrate,LiOD-D2O),thedeuteriuminpoundactsasamoderator,slowingdowntheneutronstothermalenergiesafterjustfewcentimeters:inthiswaywecanavoidtheproblemsrelatedtoanexternalmoderator.Wealsoconsideredaliquidconverter,usingasolutionofLiODinheavywater;itismoreefficientforaverysmallamountoflithium,howeverthelargeramountofHinpound(duetotheicimpuritiesofD)reducestheoverallefficiency.Finally,wetestedaFLiBeconverter,whichwassuggestedforIsoDAR@KamLAND[2].Whentheingneutronenergyishigh(≥50MeV)FLiBeismoreefficientthanLiOD,duetotheneutronmultiplicationeffect(i.e.additionalneutronscanbeknockedoutfromDorBeatoms).Howeverusuallyiftheneutronsareproducedusingaprotonbeamthefractionofhigh-energyneutronsisverysmall(morethan90%arebelow10MeV).ThismeansthattheoverallefficiencyofFLiBeinthecasesconsideredislowerthanLiOD’s(thiscouldchange,however,iftheneutronenergyspectrumisdifferent,forexampleifadeuteronbeamisused)(Fig.1). Fig.1(coloronline)8Liyieldusinga25MeV(leftpanel)or250MeV(rightpanel)protonbeam. 2017 IMP&HIRFLAnnualReport TheseresultswerepublishedinEur.Phys.J.C,77(2017)12,864. References [1]
E.Ciuffoli,
J.Evslin,
F.Zhao,JHEP,1601(2016)004.[2]
M.Abs,etal.,arXiv:1511.05130[-ph]. ·17· ∗Foundationitem:NationalNaturalScienceFoundationofChina(11575254) 1-12GlueballinQCDSumRules∗ AlexandrPimikovandZhangPengming Thelowestdimensionthree-gluoncurrentsthatcoupletotheexotic0±−glueballshavebeenconstructedusingthehelicityformalism.Basedontheconstructedcurrents,weobtainnewQCDsumrules(SRs)thathavebeenusedtoextractthemassesandthedecayconstantsofthescalarexotic0±−glueballs.Weestimatethemassesforthescalarstateandforthepseudoscalarstatetobe m+=9.8+−11..34GeVandm−=6.8+−11..12GeV. TheresultshavebeenpublishedinRefs.[1-3].Thehelicitybasedcurrentconstructionhavebeenusedtobuildnewthree-gluoncurrentsofminimaldimension thatcoupletothe0±−glueballstates.Inourworks,aconsistentSRsfortheexoticglueballswereobtainedusingconstructedcurrents.WehavecalculatedOPEofthecorrelatorsuptodimension-8whichcoupletothispuregluonstates,andhaveshowedthatthereisgoodstabilityfortheSRs.FromthesestableSRs,wecalculatedthepredictionsforthemassesofexotic0±−glueballs.Ourresultonthemassoftheexotic0−−glueballisinqualitativeagreementwiththeresultoflatticeQCD. TheBelleCollaborationhasperformedasearchintherangeofmasseslowerthanourpredictedmassandfoundnoevidencefortheexotic0−−glueball.ArecentstudywithinQCDSRfortheexotic0−−tetraquarkwithlightquarkcontentpredictedasmallmass,(1.66±0.14)GeV.Therefore,thelargemassdifferenceshouldleadtoaverysmallmixingbetweenthislighttetraquarkstateandtheheavyexotic0−−glueball.However,onecannotavoidthediscussionaboutpossiblemixingbetweentheexoticglueballstatesandtheheaviertetraquarksofthesameexoticquantumnumber,ifsuchheavytetraquarksexist.Butwewouldliketopointoutthattoourknowledge,allestimationswithinvariousmodelsgivethevalueofthemassforthehidden-charmtetraquarkstobearound4GeV,whichisrathersmallparisontoourglueballmasses(Fig.1). Fig.1(coloronline)GlueballmassesfromQCDSRandlatticeresultsfor0−−stateparisonwithourresultsfor0±−glueballs. Thedecayofthethree-gluonstatetothehadronsissuppressedbythelargepowerofthestrongcouplingatthevirtualityoftheglueball’sgluonsQ2∼4GeV2,whereweassumethatthegluonscarryequalmomenta.Oneoftheallowedchannelsincludescharmoniuminthefinalstate.Inparticular,weconsidertheS-wavedecayofglueballG(0−−)→f1(1285)+J/Ψtobethemostpreferableduetothelargeglueballmassandthesmallwidthsofthefinal
1.Checkingtheintegralenergyandbaryoncharge,wefindthattheboundaryindeedseparatesn=2solutionintotwoskyrmioinswithsameenergyandbayronchargeandthiscouldbeviewedasshellstructureinabaryon. References [1]
Y.M.Cho,KyoungtaeKimm,
J.H.Yoon,etal.,Eur.Phys.J.C,77(2017)88.[2]
T.H.R.Skyrme,Proc.Roy.Soc.(London),260(1961)127;262(1961)237;Nucl.Phys.,31(1962)556.[3]
C.Adam,S´anchez-Guill´enJ,
A.Wereszczyn´ski,Phys.Rev.D,82(2010)085015. ∗Foundationitem:NationalNaturalSciencefoundationofChina(11575254,11475227). 1-11GettingtheMostNeutrinosoutofIsoDAR∗
E.Ciuffoli,
H.Mohammed,
J.Evslin,
F.Y.ZhaoandM.Deliyergiyev SeveralexperimentsintendtouseneutrinosproducedviaeDecayAtRest(IsoDAR)tosearchforsignsofthepresenceofsterileneutrinos.InmostIsoDARexperimentsspallationneutronsareabsorbedina7Lisleeve(converter),creating8Li,thatwilldecayemittingν¯e.OftenIsoDARproposalsplantouseexistingdetectorsorelerators,toreducethecostoftheexperiment.Inparticular,ithasbeenproposedtouseasaneutronsourcethehigh-intensityprotoneleratorsthatwillbebuiltasapartoftheChinaeleratorDrivenSystem(C-ADS)program[1]. UsingGeant4andFLUKAsimulations,westudiedtheoptimizationofthetargetstation,focusinginparticularontheneutronyieldandonthe8Liproduction.Ifthetargetissurroundedbyaconverteroramoderator,theneutronscanbounceback.Thisisaproblemespeciallyinthecaseofheavymetaltargets,whichhavealargeneutronabsorptioncrosssection:inthecaseofW,upto40%oftheneutronscanbelostduetothebounceback.Wefoundoutthatthiseffectcanbereducebyplacingagap(vacuumsleeve)betweenthetargetandtheconverter.Forexample,witha20cmgaptheneutronlosscanbedecreaseddowntolessthan20%. Inordertobeabsorbedintheconverter,theneutronsmustbefirstsloweddowntothermalenergies.InthefirstIsoDARproposal,forthispurposeaheavywatersleeve(moderator)wasplacedbetweenthetargetandtheconverter;howeverinthiswayeithermostofneutronsarenotthermalizedorasignificantfractionofthemisabsorbedinsidethemoderator.Apossiblesolutionistomixthemoderatorwiththeconverter.Forexample,usinglithiumdeuteroxide(eitherinitsanhydrousform,LiOD,ormonohydrate,LiOD-D2O),thedeuteriuminpoundactsasamoderator,slowingdowntheneutronstothermalenergiesafterjustfewcentimeters:inthiswaywecanavoidtheproblemsrelatedtoanexternalmoderator.Wealsoconsideredaliquidconverter,usingasolutionofLiODinheavywater;itismoreefficientforaverysmallamountoflithium,howeverthelargeramountofHinpound(duetotheicimpuritiesofD)reducestheoverallefficiency.Finally,wetestedaFLiBeconverter,whichwassuggestedforIsoDAR@KamLAND[2].Whentheingneutronenergyishigh(≥50MeV)FLiBeismoreefficientthanLiOD,duetotheneutronmultiplicationeffect(i.e.additionalneutronscanbeknockedoutfromDorBeatoms).Howeverusuallyiftheneutronsareproducedusingaprotonbeamthefractionofhigh-energyneutronsisverysmall(morethan90%arebelow10MeV).ThismeansthattheoverallefficiencyofFLiBeinthecasesconsideredislowerthanLiOD’s(thiscouldchange,however,iftheneutronenergyspectrumisdifferent,forexampleifadeuteronbeamisused)(Fig.1). Fig.1(coloronline)8Liyieldusinga25MeV(leftpanel)or250MeV(rightpanel)protonbeam. 2017 IMP&HIRFLAnnualReport TheseresultswerepublishedinEur.Phys.J.C,77(2017)12,864. References [1]
E.Ciuffoli,
J.Evslin,
F.Zhao,JHEP,1601(2016)004.[2]
M.Abs,etal.,arXiv:1511.05130[-ph]. ·17· ∗Foundationitem:NationalNaturalScienceFoundationofChina(11575254) 1-12GlueballinQCDSumRules∗ AlexandrPimikovandZhangPengming Thelowestdimensionthree-gluoncurrentsthatcoupletotheexotic0±−glueballshavebeenconstructedusingthehelicityformalism.Basedontheconstructedcurrents,weobtainnewQCDsumrules(SRs)thathavebeenusedtoextractthemassesandthedecayconstantsofthescalarexotic0±−glueballs.Weestimatethemassesforthescalarstateandforthepseudoscalarstatetobe m+=9.8+−11..34GeVandm−=6.8+−11..12GeV. TheresultshavebeenpublishedinRefs.[1-3].Thehelicitybasedcurrentconstructionhavebeenusedtobuildnewthree-gluoncurrentsofminimaldimension thatcoupletothe0±−glueballstates.Inourworks,aconsistentSRsfortheexoticglueballswereobtainedusingconstructedcurrents.WehavecalculatedOPEofthecorrelatorsuptodimension-8whichcoupletothispuregluonstates,andhaveshowedthatthereisgoodstabilityfortheSRs.FromthesestableSRs,wecalculatedthepredictionsforthemassesofexotic0±−glueballs.Ourresultonthemassoftheexotic0−−glueballisinqualitativeagreementwiththeresultoflatticeQCD. TheBelleCollaborationhasperformedasearchintherangeofmasseslowerthanourpredictedmassandfoundnoevidencefortheexotic0−−glueball.ArecentstudywithinQCDSRfortheexotic0−−tetraquarkwithlightquarkcontentpredictedasmallmass,(1.66±0.14)GeV.Therefore,thelargemassdifferenceshouldleadtoaverysmallmixingbetweenthislighttetraquarkstateandtheheavyexotic0−−glueball.However,onecannotavoidthediscussionaboutpossiblemixingbetweentheexoticglueballstatesandtheheaviertetraquarksofthesameexoticquantumnumber,ifsuchheavytetraquarksexist.Butwewouldliketopointoutthattoourknowledge,allestimationswithinvariousmodelsgivethevalueofthemassforthehidden-charmtetraquarkstobearound4GeV,whichisrathersmallparisontoourglueballmasses(Fig.1). Fig.1(coloronline)GlueballmassesfromQCDSRandlatticeresultsfor0−−stateparisonwithourresultsfor0±−glueballs. Thedecayofthethree-gluonstatetothehadronsissuppressedbythelargepowerofthestrongcouplingatthevirtualityoftheglueball’sgluonsQ2∼4GeV2,whereweassumethatthegluonscarryequalmomenta.Oneoftheallowedchannelsincludescharmoniuminthefinalstate.Inparticular,weconsidertheS-wavedecayofglueballG(0−−)→f1(1285)+J/Ψtobethemostpreferableduetothelargeglueballmassandthesmallwidthsofthefinal
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