The discovery potential for the MSSM with heavy scalars at the LHC in the
case of light inos is examined. We discuss the phenomenology of the model and
the observables to determine the parameters. We show that for light gauginos,
the model parameters can be constrained with a precision of the order of 15%.Comment: contribution to the Electroweak session of the Moriond 2008
  conferenc

Turlay, Emmanuel

English

arXiv

The discovery potential for the MSSM with heavy scalars at the LHC in the case of light inos is examined. We discuss the phenomenology of the model and the observables to determine the parameters. We show that for light gauginos, the model parameters can be constrained with a precision of the order of 15%.The discovery potential for the MSSM with heavy scalars at the LHC in the case of light inos is examined. We discuss the phenomenology of the model and the observables to determine the parameters. We show that for light gauginos, the model parameters can be constrained with a precision of the order of 15%

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arXiv:0805.2272v1  [hep-ph]  15 May 2008T H E M SSM W IT H D EC O U P LED SC A LA R S AT T H E LH CE.TURLAYaLaboratoire de l’Accelerateur LineaireUniversite Paris-Sud 11,91898 Orsay cedex,FranceThediscovery potentialfortheM SSM with heavy scalarsattheLHC in thecaseoflightinosis exam ined. W e discuss the phenom enology ofthe m odeland the observables to determ inethe param eters. W e show thatfor light gauginos,the m odelparam eters can be constrainedwith a precision ofthe orderof15% .1 IntroductionAssum ing a large soft{breaking scale forthe M SSM scalars1;2;3;4;5 pushessquarks,sferm ionsand heavy Higgsesoutofthekinem atic reach ofthe LHC withouta ecting thegaugino sector.The hierarchy problem willnotbe solved withoutan additionallogarithm ic  ne tuning oftheHiggs sector. Nevertheless,a m odelcan be constructed to provide a good candidate for darkm atterand realizegrand uni cation whilem inim izing proton decay and FCNCs.W einvestigatethe LHC phenom enology ofthe m odel,where allscalars are decoupled from the low energyspectrum . W e focus on gaugino{related signatures to estim ate the accuracy with which itsunderlying param eterscan bedeterm ined.2 P henom enologyThe spectrum at the LHC is reduced to the gauginos,Higgsinos and the light Higgs. At theinterm ediate scale M S the e ective theory ism atched to the fulltheory and the usualM SSMrenorm alization group equationsapply. The Higgsino m assparam eter and the ratio tan inthe Higgssectorcorrespond to theirM SSM counterparts.Thegauginosm assesM 1;2;3 and theHiggs-sferm ion-sferm ion couplings unify,and M S replaces the sferm ion and the heavy Higgs’aThiswork wasdonein collaboration with D .Zerwas(LAL-O rsay,Fr),N.Bernaland A.D jouadi(LPT-O rsay,Fr),M .Rauch and T.Plehn (U.ofEdim burg,UK )and R.Lafaye (LAPP-Annecy,Fr)~g~g 68 pb ~ ~g 311 fb~ ~0 12 pb ~0~g 223 fb~ ~ 6 pb ~0~0 98 fbTotal 87 pbTable 1:NLO crosssectionsforSUSY pairproduction atthe LHC.m assparam eters.Thissetresem blesthem SUG RA param etersetexceptfortan now playingtherole ofa m atching param eter(with theheavy Higgsesbeing decoupled)ratherthan thatofan actualvev ratio6.W eselectourparam eterpointaccording to threeconstraints: rst,wem inim izetheam ountof netuning necessary to bring thelightHiggsm assinto the100 to 200 G eV rangeand reduceM S to 10 TeV,stillwelloutside the LHC m assrange. The m ain reason forthis low breakingscaleisthatwewantthegluino to decay insidethedetector(preferably attheinteraction point)instead ofbeing long{lived8;4.Secondly,we obtain the correct relic dark{m atter density  h2 = 0:111+ 0:006  0:00810 by setting = 290 G eV and M 2(M G U T)= 132:4 G eV orM 2(M weak)= 129 G eV.Thiscorrespondsto thelight{Higgs funnelm LSP  M 2=2  M h=2,where the s-channelHiggs exchange enhances theLSP annihilation rate.And  nally,mh needsto bewellabove theLEP lim it,which we achieveby choosing tan = 30. W e obtain m h = 129 G eV,m ~g = 438 G eV,chargino m asses of117and 313 G eV,and neutralino m asses of60,117,296,and 310 G eV with a m odi ed version ofSuSpect5;11,decoupling theheavy scalarsfrom theM SSM RG Es. ~02and ~1aswellas ~04and~2are degenerate in m ass. Allsupersym etric particlesand m ostnotably the gluino are m uchlighterthan in theSPS1a param eterpointItisim portantto notethatthisfeatureisspeci ctoour choice ofparam eters and not generic in heavy{scalar m odels. As a consequence,allLHCproduction crosssectionsare greatly enhanced with respectto SPS1a.Table 1 shows the m ain (NLO ) cross sections at the LHC from Prospino212;13;14. TheSUSY production is dom inated by gluino pairs whose rate is eight tim es that ofthe SPS1apoint:thelowergluinom assenlargestheavailablephasespace,whilein addition thedestructiveinterferencebetween sand t{channeldiagram sisabsent.Thesecond largestprocessisthe ~1~02production,which givesrise to a 145 fb ofhard-jetfree,e and  trilepton signal,m ore than ahundred tim esthatofthe SPS1a point.3 O B SERVA B LESThe  rstobviousobservable isthe lightHiggsm assmh.Although slightly higherthan in m ostM SSM points,m h can stillbem easured in theHiggsto two photonsdecay15 (m h < 150 G eV).Thesystem atic erroron thism easurem entism ainly dueto theincertainty on theknowledgeofthe electrom agnetic energy scale.A m easurem ent ofthe gluino pair production cross section appears feasible and could bevery helpfulto determ ineM 3.Thebranching ratio ofgluinosdecaying through a virtualsquarkinto a chargino or a neutralino along with two jets is 85% . The chargino willin turn decaym ostly into the LSP plus two leptons or jets. Such events would feature at least 4 high-pTjets,a largeam ountofm issing energy dueto thetwo ~01in the nalstate and possibly leptons.The m ain backgrounds for such signatures are tt pairs,W + jets and Z+ jets with respectiveproduction rates of830 pb,4640 pb and 220 pb 16. Despite these large cross sections,m ostofthe background can be elim inated by applying standard cutson =E T,the num berofhigh-pTjetsaswellasthee ective m assb which wechecked using a fastLHC-likesim ulation.Them ainbM e = =E T +PpT (jets).sourceofsystem aticerrorsforthisobservableisthe5% erroron theknowledgeofthelum inosity.W e take the theoreticalerroron thecalculation ofthe crosssection to beroughly 20% .Thenextobservableisthetrilepton signal.Aftergluino pairs,thenextdom inantchannelisthedirectproduction of~1~02.22% of~1sdecay through a virtualW into an electron orm uonand a neutrino and the LSP.Sim ilarly,7% of ~02sdecay through a virtualZ into an O pposite-Sign-Sam e-Flavourlepton pair(O SSF)and theLSP.Theresulting signalfeaturesthreeleptonsam ong which two are O SSF,a large am ountofm issing transverse energy due to the two LSPsplusthe neutrino and no jetin the hard process. The background forthissignature ism ainlyW Z and ZZ in which one ofthe leptonswas non-identi ed oroutside acceptance. Accordingto PYTHIA the lepton production (e and ) rates are 386 fb for W Z and 73 fb for ZZ. Thetrilepton signalhasa rateof145 fb,using SDECAY17 forthecalculation ofthebranching ratios.Including identi cation e cienciesof65% forelectronsand of80% form uons18 gives ratesof110 to 211 fb forthe background and 40 to 74 fb forthe signalbefore any cut. A study withfulldetectorsim ulation and reconstruction would provide a betterunderstanding ofsignalandbackground.Asin thepreviouscase,them ain sourceofsystem atic errorsistheuncertainty onthe lum inosity. W e also take the theoreticalerroron the value ofthe trilepton crosssection toberoughly 20% .W ithin thistrilepton signalliesanotherobservable.10% of~02sdecay into an O SSF leptonpairand theLSP.Thedistribution oftheinvariantm assofthepairfeaturesa kinem atic upperedgewhosevalueism~02  m~01.Such an observablegivespreciousinform ation on theneutralinosector and hence on M 1. The system atic error is dom inated by the lepton energy scale. Thestatistical error was extracted from a ROOT  t of the M‘‘ distribution and we estim ate thetheoreticalaccuracy to beofthe orderof1% .Thelastobservablewe usein thisstudy istheratio ofgluino decaysincluding a bquark tothose notincluding a b.A system atic errorof5% dueto the tagging ofb-jetsand a theoreticaluncertaintiesof20% areassum ed.O bservables Exp.system atic errors Statisticalerrors TheoreticalValue Error Source 100 fb  1m h 128.8 G eV 0.1% energy scale 0.1% 4%m~02  m~0157 G eV 0.1% energy scale 0.3% 1%(3‘) 145.2 fb 5% lum inosity 3% 20%R(~g ! b=!b) 0.11 5% b-tagging 0.3% 20%(~g~g) 68.2 pb 5% lum inosity 0.1% 20%Table 2:Sum m ary ofthe observablesand the corresponding errors.Table2 sum m arisesthevalueand erroroftheobservablesassum ed in thisstudy.Thethirdand fourth colum nsgive theexperim entalsystem atic errorsand theresource.The fth colum ngives the statisticalerrors for an integrated lum inosity of100 fb  1 corresponding to one yearofdata-taking at the LHC nom inallum inosity. The last colum n gives an estim ation ofthetheoreticaluncertainties.4 PA R A M ET ER D ET ER M IN AT IO NW eusedi erentsetsoferrorsforthe ts.Firstwedeterm inetheparam etersin thelow statisticscenario ignoring theoreticaluncertainties. Second we assum e an in nite statistic and there-fore assum e negligeable statisticalerrorsto estim ate the ultim ate precision barrierim posed byexperim entalsystem atic errors. Finally the e ect oftheoreticaluncertainties is estim ated byincluding them into the previousset.W e expectthese to dom inate.W ith noinform ation on thesquark and sferm ion sectoratall,exceptfornon-observation,weareforced to  x MS and A tand setM 2 to beequalto M 1.W e ttheparam etersto theobservablesusing the Minuit  tter.Them inim um ofthe 2 isfound by MIGRAD.W e startfrom a pointfarfrom thenom inalvalues(fM 1;M 3;tan;g = f100;200;10;320g)and reach thevaluesreportedin table 3.Errorsare determ ined with MINOS.Theoreticalerrorsare treated asG aussian.Param eter Nom .values Fitvalues Low stat. 1 stat. 1 stat.+ thM S 10 TeV  xedA t 0  xedM 1 132.4 G eV 132.8 G eV = M 2M 2 132.4 G eV 132.8 G eV 6 5% 0.24 0.2% 21.2 16%M 3 132.4 G eV 132.7 G eV 0.8 0.6% 0.16 0.1% 5.1 4%tan 30 28.3 60 undet. 1.24 4% 177 undet. 290 G eV 288 G eV 3.8 1.3% 1.1 0.4% 48 17%Table 3:Resultofthe ts.Errorson the determ ination oftheparam eterare given forthethree errorsets.Bothabsolute and relative valuesare given.Table 3 showsthe resultofthe  tsin both absolute and relative values.Itisinteresting tonotethattan in undeterm ined exceptin thecaseofin nitestatisticaland theoreticalaccuracy.Thequality ofthetrilepton and gluino signalsgivesvery good precision on thedeterm ination ofM 1 and M 3 even with low statisic. The inclusion oftheoreticaluncertainties indeed decreasesthe accuracy butstillallows for a determ ination. M 3 only dependson the large gluino signaland itsdecays,explaining itsrelative stability.M 1 and M 2 seethelargestim pactoftheoreticalerrors. Thisisbecause they depend on  rstorderon the trilepton cross-section and on secondorderon thebto non bgluino decaysratio both ofwhich beara large theoreticalerror.5 C O N C LU SIO NTheM SSM with heavy scalarscan very wellsatisfy currentexperim entaland theoreticallim itson physics beyond the standard m odeland also solve a good num ber ofissues present in thetraditionnalM SSM .W e described itsphenom enology atthe LHC in the case oflightinosandshowed thatsuch a sim ple and lightspectrum could lead to very high production ratesm akingthem odeldiscoverable.Them ain observablechannelsaregluinopairsand thetrilepton channelwhose hard-jet free channelm akes it welldistinct from SM and SUSY backgrounds. O therobservables such as the light Higgs m ass,the jm~02  m~01jkinem atic edge and the b to non bproducing gluino decayscould lead to a determ ination ofm ostparam etersto the levelofa fewpercentwith 100 fb  1 ignoring theoreticalerrors.In a m orerealistic picturewhereweassum ednon-zero theoreticalerrors,wesaw thatm ostparam eterscan bedeterm ined with a precision of15% .W e also saw thatthescalarsection including tan could only bepoorly determ ined ifatall.New com plem entary observablescould help determ ine betterthe scalarsector. Equally,a lookat other param eter points willprovide a m ore com plete view ofthe discovery potentialofaM SSM with decoupled scalarsatthe LHC.R eferences1. N.Arkani-Ham ed and S.Dim opoulos,JHEP 06 (2005)073,[hep-th/0405159].2. G .F.G iudice and A.Rom anino,Nucl.Phys.B 699 (2004)64{89,[hep-ph/0406088]3. J.D.W ells,Phys.Rev.D 71 (2005)015013,[hep-ph/0411041].4. W .K ilian,T.Plehn,P.Richardson and E.Schm idt,Eur. Phys. J.C 39 (2005) 229{243,[hep-ph/0408088].5. N. Bernal, A. Djouadi and P. Slavich, JHEP 07 (2007) 016, [arXiv:0705.1496[hep-ph]].6. M .Drees[hep-ph/0501106].7. S.W einberg,Phys. Rev.Lett.59 (1987)2607.8. A.C.K raan,Eur.Phys. J.C 37 (2004)91-104,hep-ex/0404001.9. G .R.Farrarand P.Fayet,Phys.Lett.B 76 (1978)575-579.10. D. N. Spergel et al., W M AP Collaboration, Astrophys. J. Suppl. 170 (2007) 377,astro-ph/0603449.11. A.Djouadi,J.-L.K neurand G .M oultaka,Com put.Phys.Com m un.176 (2007)426-455,hep-ph/0211331.12. W .Beenakker,R.Hopker,M .Spira and P.M .Zerwas,Nucl. PhysB 492 (1997)51-103,hep-ph/9610490.13. W .Beenakkeretal.,Phys.Rev.Lett.83 (1999)3780-3783,hep-ph/9906298.14. T.Plehn,(1998),hep-ph/9809319.15. M .Bettinellietal.,ATL-PHYS-PUB-2007-013 (2007).16. ATLAS Collaboration,TDR vol.2 CERN-LHCC-99-15 (1999)469.17. M .M uhlleitner,Acta Phys.Polon.B 35 (2004)2753-2766,hep-ph/0409200.18. ATLAS Collaboration,AtlasTechnicalPaper.

The MSSM with decoupled scalars at the LHC

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