Stop-Stop-Higgs Production at future Linear Collider

In the Minimal Supersymmetric Standard Model, the cross section for the associated production of the lightest neutral Higgs boson with the lightest top squark pairs can be rather substantial at high energies. We summarize the properties of this production

PM/99–37

STOP–STOP–HIGGSPRODUCTION9

991 tcO 7 1v9620199/hp-pe:

h

v

i

XraATFUTURELINEARCOLLIDER

A.DJOUADI,J.-L.KNEURaandG.MOULTAKAPhysiqueMath´ematiqueetTh´eorique,UMRNo5825–CNRS,Universit´eMontpellierII,F–34095MontpellierCedex5,France

IntheMinimalSupersymmetricStandardModel,thecrosssectionfortheassoci-atedproductionofthelightestneutralHiggsbosonwiththelightesttopsquarkpairscanberathersubstantialathighenergies.Wesummarizethepropertiesofthisproductionprocessatafuturee+e linearcollider,includingtheγγmode.

1Introduction

IntheMinimalSupersymmetricStandardModel(MSSM)1,ifthemixingbetweenthirdgenerationsquarksislarge,stops/sbottomscanberatherlight2andatthesametime,theircouplingtoHiggsbosonscanbecomesubstantial.ThismighthavearatherlargeimpactonthephenomenologyoftheMSSMHiggsbosons3 7.Moreprecisely,concentratingonscalartopquarks,theirmasseigenvaluesaregivenby

m2 212 222t1,2=mt+(m2QL

m t

R

+···)+4mtAt ,(1)wheremQ L,m t

Rarethesoft-SUSYbreakingscalarmassesandthedotsstandfortheD–terms∝MandtheZ2

cos2β.Inthedecouplinglimit(thelightesthbosonisStandardModellikeotherbosonsA,HandH±,areveryheavy),theexpressionsthecouplinght 1t

of

1simplyreads(θtisthemixingangleandsW≡sinθW) 1 t1 13sWcos2θt +m2gmtA tht=cos2β2

t2

sin2θt

aSpeaker

In the Minimal Supersymmetric Standard Model, the cross section for the associated production of the lightest neutral Higgs boson with the lightest top squark pairs can be rather substantial at high energies. We summarize the properties of this production

notconsiderotherHiggsproductionprocesseswithe.g.theheavyHorAbosonsproducedinassociationwithtopsquarks.Forlargemasses,theseprocesseswillbesuppressedbyphase–spacewellbeforethedecouplingregimeisreached.2

Associatedproductionate+e colliders

Atfuturelineare+e colliders,the nalstate t

1t 1hmaybegeneratedinthreeways:(i)two–bodyproductionofamixedpairoftopsquarksandthedecayoftheheavieststoptothelighteste+e annihilatione+e oneandaHiggsboson,(ii)thecontinuumproductionin

1γγ→ t

1t 1h.→t

t 1hand(iii)thecontinuumproductioninγγcollisions2.1Two–bodyproductionanddecay

Thetotalcrosssection11fortheprocess(i)should,inprinciple,belargeforthe nalstatetobecopiouslyproduced.However,σ(e+e 1 enough

t2)involvestheZ t1t 2coupling,proportionaltosin2θt,whilethe|ght →t

theparameterspaceisproportionaltocos2θ1t

2t,suchthatthe|couplingcrosssectioninmosttimesofbranchingratiowillbeverysmallinthenomixing[|θt [θt2smaller|～π/4]thancases.the t

[In2decayaddition,widthstheintodecaycharginowidtht

11and→～0]neutralinos].ht 1andisinmaximalgeneralmixing

muchNevertheless,thereareregionsoftheMSSMparameterspacewherethecombinationsin2θtcos2θtcanbelarge;thisoccurstypicallyforanottoosmallmt ×moderateA L–mt

Rsplittingandtvalues.5Inthiscase,whichisoftenrealizedinthemSUGRAscenario,thismechanismisvisiblefortheexpectedhighluminosities12

Ldt～500fb 1ThisisillustratedinFig.1,wherethecrosssectione+ branching√ratioBR( e 1 .

t2timesthet

2→t 1h)isshownasafunctionofthet →t

1massatac.m.energyof

In the Minimal Supersymmetric Standard Model, the cross section for the associated production of the lightest neutral Higgs boson with the lightest top squark pairs can be rather substantial at high energies. We summarize the properties of this production

2.2

Productioninthecontinuumine+e collisions

Thecrosssectionfortheprocesse+e anyofthetwosquarkshas→q iq iΦwithΦtheCP–evenHiggsbosonhorH,andq ibeencalculatedin5.WeshowinFig.2

theratesfor√the t1 t1h nalstateasafunctionofthe t1massintheunconstrained

MSSM,at

In the Minimal Supersymmetric Standard Model, the cross section for the associated production of the lightest neutral Higgs boson with the lightest top squark pairs can be rather substantial at high energies. We summarize the properties of this production

1t 1h)[infb]at√Figure3:σ(γγ→t

sγγ<～0.8

√

s>～500GeVandwithveryhighluminosities

1t 1hcanleadtoseveralhundredsofevents,Ldt～500fb 1,theprocesse+e →t

sincethecrosssectionscanexceedthelevelofa1fbfornottooheavytopsquarks

t>1TeV.Inthecasewherethetopsquarkdecaysandlargetrilinearcoupling,A～

intoabquarkandareal/virtualchargino,the nalstatetopologywith4bquarks,missingenergyandadditionaljetsorleptonswillberatherspectacularandshouldbeeasytobeseenexperimentally,thankstothecleanenvironmentofthesecolliders.

In the Minimal Supersymmetric Standard Model, the cross section for the associated production of the lightest neutral Higgs boson with the lightest top squark pairs can be rather substantial at high energies. We summarize the properties of this production

Intheγγoptionofthee+e collider,thecrosssectionsaresimilaraspreviouslyfarfromtheparticlethresholds,butaresuppressedforlargermassesbecauseofthereducedc.m.energies;forγγluminositiesofthesameorderastheoriginale+e

1t 1h nalstateshouldalsobeobservableinthismode,atleastinluminosities,thet

someareasoftheMSSMparameterspace.

1h nalstateisdirectlyproportionalto 1tTheproductioncrosssectionofthet

1t 1hcouplings,thereforestudyingthisprocesswillallowtomea-thesquareofthet

surethisimportantcouplingandtoprobedirectlysomeofthesoft–SUSYbreakingparameters.References

1.Forreviewssee:H.P.Nilles,Phys.Rep.110,1(1984);H.E.Haber,G.L.Kane,Phys.Rep.117,75(1985);S.P.Martin,hep-ph/9709356,inPerspectivesinSupersymmetry,ed.byG.L.Kane,WorldScienti c.

2.J.Ellis,S.Rudaz,Phys.Lett.B128(1983)248;M.Drees,K.Hikasa,Phys.Lett.B252(1990)127.

3.A.Djouadi,Phys.Lett.B435(1998)101;A.Djouadietal.,Eur.Phys.J.C1(1998)149andEur.Phys.J.C1(1998)163.

4.A.Djouadi,J.L.Kneur,G.Moultaka,Phys.Rev.Lett.80(1998)1830.5.A.Djouadi,J.L.Kneur,G.Moultaka,hep-ph/9903218.6.G.B´elanger,F.Boudjema,T.Kon,fage,Eur.Phys.J.C9(1999)511;G.B´elanger,F.Boudjema,K.Sridhar,hep-ph/9904348.7.A.Dedes,S.Moretti,hep–ph/9812328andhep-ph/9904491.

8.Z.Kunszt,Nucl.Phys.B247(1984)339;J.Dai,J.F.Gunion,R.Vega,Phys.Rev.Lett71(1993)2699;D.Froidevaux,E.Richter-Was,Z.Phys.C67(1995)213;Z.Kunszt,S.Moretti,W.J.Stirling,Z.Phys.C74(1997)479;M.Spira,Habilitationthesis,hep–ph/9705337.

9.A.Djouadi,J.Kalinowski,P.Zerwas,Z.Phys.C54(1992)255andMod.Phys.Lett.A7(1992)1765;S.Dittmaieretal.,Phys.Lett.B441(1998)383;S.Dawson,L.Reina,Phys.Rev.D57(1998)5851;S.Moretti,hep–ph/9902214.

10.H.Georgietal.,Phys.Rev.Lett.40(1978)692;A.Djouadi,M.Spira,P.M.

Zerwas,Phys.Lett.B264(1991)440;S.Dawson,Nucl.Phys.B359(1991)283;M.Spiraetal.,Nucl.Phys.B453(1995)17;S.Dawson,A.Djouadi,M.Spira,Phys.Rev.Lett.77(1996)16.

11.E.Accomandoetal.,Phys.Rept.299(1998)1;A.Bartletal.,hep–

ph/9804265.

12.Seee.g.thetalkofR.Brinkman,theseproceedings.

13.ForareviewonCCBconstraintsseee.g.J.A.Casas,A.Lleyda,C.Mu noz,

Nucl.Phys.B471(1996)3,andreferencestherein.14.M.Drees,K.Hagiwara,Phys.Rev.D42(1990)1709.

15.Seeforinstance,G.Altarelli,hep–ph/9611239;J.Erler,ngacker,hep–

ph/9809352;G.C.Choetal.,hep–ph/9901351.

16.I.F.Ginzburgetal.,Nucl.Instr.Meth.205(1983)47and219(1984)5;V.I.

Telnov,Nucl.Instr.Meth.A294(1990)72andA335(1995)3.17.C.Boehm,A.Djouadi,Y.Mambrini,hep-ph/9907428.

本文来源：https://www.bwwdw.com/article/0jjj.html