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Searches for Neutral Higgs Bosons in Supersymmetric Extensions of the SM

Searches for Neutral Higgs Bosons in Supersymmetric Extensions of the SM. Markus Schumacher Klausurtagung Feldberg, 13. 12. 2008. Standard Model (SM) Minimal Supersymmetric Extension of the SM (MSSM) Next-to-Minimal Supersymmetric Extension of the SM (NMSSM).

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Searches for Neutral Higgs Bosons in Supersymmetric Extensions of the SM

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  1. Searches for Neutral HiggsBosons in SupersymmetricExtensionsofthe SM Markus Schumacher Klausurtagung Feldberg, 13. 12. 2008 • Standard Model (SM) • Minimal Supersymmetric • Extension ofthe SM (MSSM) • Next-to-Minimal Supersymmetric • Extension of the SM (NMSSM) • Motivation • StructureofHiggsSector • TheoreticalConstraints • Status of Searches • Prospects for Discovery

  2. Theoretical constraints Particle masses and their “problem” • Experiment: all particles massive (except g + gluon) • Theory: forces described via gauge symmetries • Problem: SU(2)LxU(1)Y-Symmetrie: no masses for • - gauge bosons: W und Z • - fermiones: (l=Dublett, r=Singlett) „ad hoc“ mass terms destroy: • renormalizibility  no precision predictions e.g. mtop • good high energy behaviour: e.g. WLWL-Streuung violates unitarity at ECM ~ 1.2 TeV

  3. The Brout-Englert-Hagen-Higgs-Kibble-Mechanismus The „Standard“-Solution: doublet of 4 skalar fields with appropiately choosen potential V = -m2 |f+f| + l |f+f|2 m2,l > 0 minimum not at f=0  spontaneous symmetry breaking Higgs field has two components: 1) omnipresent, homogeneous background field v= 247 GeV 2) Higgs-Boson H with unknown mass MH ~ Ölv H restaures unitarity if gHWW ~ MW gHff ~ Mf and MH not too large

  4. Mass generation and Higgs boson couplings: F = v + H • interaction with v=247 GeV • interaction with Higgs-Boson H x x 2 v ggauge Higgs x 2 g gauge W/Z boson W/Z boson W/Z Bosonen MV~ gvgauge coupling Fermions mf~ gfv Yukawa coupling • VVH coupling ~ vev: only exists after electroweak symmetry breaking •  observation of VBF yields indirect hint to background field • only one free parameter: MH or l

  5. Theoretical constraints on the Higgs boson mass • Unitarity in VV scattering: < 1 TeV • energy /temperature dependence of quartic coupling l Leftdiagram: increasingl requirel < 1 uptoenergyL  upperbound on MH=l(MH)v triviality/pertubativitybound Rightdiagram: decreasinglif mt large requirel >0 uptoenergyL  lowerbound on on MH=l(MH)v vacuumstabilitybound

  6. Experimental constraints on MH • indirectprediction in SM: MW(Phys) = MW(Born) + t H W W W W W b 2 … mt + … ln(MH) MH < 154 (185) GeV (incl. dir. limit) • direct search at LEP: MH < 114.4 GeVexcluded at 95% CL • direct search at Tevatron: MH ~ 170 GeV excluded at 95% CL

  7. Signal rates for SM Higgs boson production Preliminary Preliminary NLO (in QCD) (except ttH) HDECAY (Djouadi,Spira et al.) HIGLU, ... (SPIRA) • Vectorboson fusion qqqqH: 2nd dominant production • but additional signature from outgoing quarks • Hbb not selectable in ggH and VBF • H tt not selectable in gg->H •  VBF Htt promising channel close to LEP limit our group: H tt ll + 4 n (l=e, m)

  8. Vektor boson fusion ppqqH with Htt  ll 4n • signal characteristics: - 2 forward jetswith rapidity gap - Higgs decay products in central detector ttll (l=e ,m): 40fb • background: reducible ---------------------------------- irreducible 833 pb NNLO:770(ll)+170(tt)pb 1.7pb (tt) MC@NLO ALPGEN/SHERPA SHERPA kinematics, colour flow, … mass reconstruction

  9. VBF:Challenges and our plans • reconstruction of taggings jets Preliminary • central jet veto (pt>20 GeV, |h|<3.2) Preliminary EW QCD • mass reco. in collinear approximation sM/M~12to 14% dominatedbyEmiss 20% worseforlowlumi. pile-up • optimise algos and study influence of pile up and underlying event • - investigate minimum bias and Zmm+jets - use of tracking information

  10. Mass distribution and background estimate • mass distribution after all cuts peak on shoulder of dominant Z BG  estimate from data needed tt H Zjj • Zjj shape from data jjZmmandjjZttmmidenticaltopology 1) select Z  mmevents 2) manipulatemstolooklike Z  tt  ll4n 3) applystandardselection • develop similar method for tt background • e.g. b-veto vs. b-tag, impact parameter cuts, …

  11. Discovery potential • VBF H tau tau • all current ATLAS studies Preliminary Preliminary • optimise selection (especially for ll final state): • - supress reducible BGs (tt much larger than in previous study) • - multivariate techniques • - sophisticated statistical tools

  12. Exclusion potential Preliminary Preliminary • for exclusion need signal efficiency and its systematic uncertainty • dominant influences by: • - jet energy scale  Z+jets • - parton shower + underlying event model  Z+jets, Minimum Bias • - central jet veto eff. from data  single top?, Z+jj?

  13. Stability of the Higgs boson mass • the hierarchy problem: why is v=246 GeV <<Mplanckor MGUT • large corrections to Higgs mass without new symmetry: fine tuning to level 10-34 needed or cut off at 1 TeV • divergence cancelled by particle with: D spin = ½, ~ same mass, same coupling if mass correction ~ O(100 GeV)  MSUSY~O(1TeV)

  14. Other arguments for SUSY • largest symmetry of a unitary, interacting field theory = • Lorentz invariance x gauge symmetry x supersymmetry • link to gravity: most string models are supersymmetric • local Supersymmetry incorporates gravity • Grand Unification (GUT) possible: • Cold Dark Matter (CDM): lightest SUSY particle (LSP) might be stable • Baryon asymmetry in universe (BAU): can maybe explained

  15. Parameters in SUSY (with R-Parity) • Minimal SUSY: one spartner for each SM particle, no new parameters • only freedom in Superpotential • „the problem“: SUSY broken in nature: (e.g. no spin 0 partner of electron) • no „real“ model for SUSY breaking yet  parametrise 105 additional parameters to describe SUSY breaking in specific models: mSUGRA, GMSB, AMSB,… ~5 parameters

  16. The MSSM Higgs Sector in the Nutshell • SUSY requires 2 Higgs doublets • – masses for up and down type fermions • - anomaly free •  5 Higgs bosons: 3 neutral + 2 charged • scalar potential w/o SUSY breaking „lH4" given by gauge couplings, no EW-symmetry breaking • scalar potenital after SUSY breaking • different m1, m2 evolution  m2 negative  triggers EW-symmetry breaking • after EWSB: two free parameters in Higgs sector (v1 + v2 = vSM) 2 2 2

  17. The MSSM Higgs Sector in the Nutshell • at Born level: - 2 parameters: tanb=v2/v1 and MA - CP conserved  2 neutral CP-even h,H + 1 CP-odd A - upper mass bound (quartic coupling = gauge couplings): Mh < MZ • large loop corrections from SUSY breaking sectoresp. top/stop mh < 133 GeV(+-3GeV) for mtop=175 GeV, MSUSY=1TeV in constrained MSSM a la LEP/LHC corrections depend on 5 SUSY parameters: Xtmixing in stop sector M0common sfermion mass at EW scale M2, SU(2) gaugino mass at EW scale, M1 from GUT relation Mgluinogluino mass mHiggs mass mixing parameter 5 parametersfixed inthe benchmark scenariosconsidered • mSUGRA: Xt, M0for Higgs and sfermion, M1/2for gauginos, sign m, tanb

  18. MSSM Higgs Bosons Phenomenologie • modified couplings gMSSM =xgSM • no coupling of A to W/Z • small a  small BR(htt,bb) • large b  large BR(h,H,Att,bb) a = mixing btw. CP-even neutral Higgs bosons • new production mode: b(b)Higgs • Higgs boson mass pattern

  19. Constraints on theHiggssector • MSSM bounds Constrained MSSM: Mh<133 GeV for mtop=175 GeV, MSUSY=1TeV General MSSM: Mh<150GeV • EW precisiondata, dark matter density, am, bsgin CMSSM = mSUGRA precisionfrom DM, am, bsgconstraints

  20. Constraints on theHiggssector: direct searches • LEP: investigated 5+3 benchmarks Mh/A<~ MZ excluded at 95% CL • TEVATRON: • largestsensitivityat large tan b • via bbH, Htt

  21. „Old“ MSSM Scans based on LO TDR and VBF-SN results 4 CPC benchmark scenarios considered: Carena et al. , Eur.Phys.J.C26,601(2003) • MHMAX scenariomaximal mh < 133 GeV  conservative LEP exclusion • Nomixing scenariosmall mh < 116 GeV  difficult for LHC • Gluophobic scenario • small gh,gluonmh < 119 GeV • Small a scenario • small ghbb and ghtt mh <123 GeV theo. aim: harm discovery via gg h, hgg and hZZ4 l theo. aim: harm discovery via VBF, htt tth, hbb • mainly influence masses and couplings of h • phenomenology of heavy states very similar

  22. Some technicalities 1) SM LO production cross sections (Spira) times MSSM correction factors (FH) Mt= 175 GeV 2) branching ratios from FeynHiggs (T. Hahn et al.) 3)efficiencies and background expectations from published „old“ MC studies 4) efficiency corrections for: (a) increased total width in MSSM w.r.t SM (b) mass degeneracy of h,H,A 5) evaluate signficance form signal and background rate counting experiment using Poissonian statistic no systematic uncertainties considered !

  23. Corrections to Expected Signal Rates a) for part of MSSM parameter space: large Gtot  eMSSM = K eSM K = h b)signal overlap due to mass degeneracy of Higgs bosons count signal in mass window 1 = signal 1 + signal 2 in window 1

  24. Vector Boson Fusion: 30 fb-1 (old LO, SN-Study) Preliminary h or H observable with 30 fb-1 • studied for MH>110GeV at low lumi running • same conclusion in other benchmark scenarios

  25. Light Higgs Boson h: 30 fb-1 observable channels: VBFbbh hmm (tth hbb w/o syst. error) Preliminary Preliminary Preliminary difference mainly due to different mh in same (tanb,MA) point ( up to 17 GeV difference)

  26. Small a scenario, h: 30 fb-1 • hole due to reduced branching ratio for H tt Preliminary Preliminary • covered by enhanced BR to gauge bosons • complementarity of search channels almost gurantees observation of h

  27. Light Higgs Boson h: 300 fb-1 (VBF only 30 fb-1) Preliminary Preliminary • also hgg, hZZ4 leptons (tthbb) contribute • large area coveredby several channels  sure discovery and parameter determination possible • small area uncovered @ mh = 90 to 100 GeV • hgg sensitive in gluophobic scenario due to VBF, Wh, tth production

  28. Heavy Neutral Higgs Bosons ATLAS preliminary • most promising: bbH/A, H/Att,mm s ~ (tanb)2 • old LO study: • tt lephad +  hadhad(M > 450 GeV) • new NLO study: tt leplep Preliminary Preliminary same BGs as VBF, Htt massreco. and BG estimate a la VBF no forwardjetand CJV but b-tag insteadof b-veto

  29. Overall discovery potential in CP conserving MSSM 300 fb-1 Preliminary • at least one Higgs boson observable for whole parameters space in all CP conserving benchmarks • significant area where only lightest Higgs boson h is observable • discrimination via - observation in SUSY cascades or H SUSY decays? - investigation of properties of h? ATLAS preliminary similar results in other benchmark scenarios VBF channels , H/Attonly used with 30fb-1

  30. SM or Extended Higgs Sector e.g. MSSM ? discrimination via VBF compare expected measurement of R in MSSM with SM prediction BR(h WW) BR(h tt) R = 300 fb-1 ATLAS prel. assumes Mh precisely known negelects syst. uncertainties D=|RMSSM-RSM|/sexp • similar study by M. Dührssen et al. incl. 13 channels and systematic uncertainties  VBF dominates

  31. The CP violating complex MSSM • MSSM Higgs sector CP conserving at Born level • CP effects via complex couplings in loops At, Ab Mgluino • mass eigenstates H1, H2, H3 not equal CP eigenstates h,A,H „new“ Born level pars: tanb and MH+- • why complex SUSY breaking parameters? • - no a priori reason why they should be real • - complex parameters yield new source of CP violation needed • - electroweak baryogenesis (1st order) in complex MSSM still ok • if mstop<mtop and MH1<120 GeV

  32. Phenomenology in the CPX scenario • H2,H3 H1H1, ZH1,WW, ZZdecays • H1,H2, H3 couple to W,Z H1 sum rule: Si gi (ZZHi) = gSM 2 2 H2 2 2 H3 • no absolute limit on mass of H1 from LEP • strong dependence of excluded region • on value for mtop • on calculation used FeynHiggs vs CPH

  33. Discovery potential in CP violating MSSM CPX scenario(Carena et al., Phys.Lett B495 155(2000)) arg(At)=arg(Ab)=arg(Mgluino)=90o,,MSUSY = 500 GeV, At=Ab=Mgluino=1 TeV, m=2TeV, M2=200GeV 300 fb-1 300 fb-1 • yet uncovered region in parameter space for light Higgs boson (not yet studied) • promising channels: ttbbH+W-bbH1W+W-bbbblnqq Higgs in SUSY cascades,….

  34. The m-problem • MSSM Superpotential • m: the only parameter with mass dimension bevor SUSY breaking • m not protectedbysymmetry, couldbe MGUT • but correct EWSB requires O(.1 to 1 TeV) • idea: replacembycondensateofnewscalarcomplexsingletfield S • whichis only coupledto MSSM Higgsfields • sevenHiggsbosons: 3 CP-even, 2-CP-odd, 2 charged • 5th neutralinofromsuperpartnerof S • severalvariants on themarket: NMSSM, MNMSSM,… • and also not SUSY singletextensions e.g. HEIDI …

  35. Investigation of sensitivity in NMSSM • following variant considered: • six free parameters at Born level: • two benchmark scenarios (Iris Rottländer, M.S. in LH07 proc. hep-ph 0803.115) (more benchmarks in PhD thesis by I. Rottländer, CERN-THESIS-2008-064) • masses, couplings, BRs calculcated with NMHDECAY (Elwanger et al.) • same procedure as for „old“ MSSM scans (i.e. LO cross sections, TDR etc. efficiencies and background numbers)

  36. Phenomenology in light A1 scenario • MH1 ~ 120 GeV and SM-like • H3,A2,H+- too heavy • MH2 ~ heavy and decoupled in unexcluded region • MA1 < MH1 /2 in almost whole plane • BR(A1 tt) • BR(H1A1A1)

  37. Discovery potential in light A1 scenario • H1 discovery potential • H2 sensitvity Preliminary Preliminary H2 photons reach limited by BR(H1A1A1) ~ 55% contour H2 only in excluded region observable • other Higgs bosons too heavy or decoupled to be observable • need dedicated searches for HA1A1bbbb,bbtt,tttt or maybe sensitivity in SUSY decays

  38. Plans for (N)MSSM Scans • create database for masses, couplings, BRs for various benchmark scenarios • provide consistent NLO cross sections - simple scaling not always thrustworthy (e.g. gluon fusion) - check approximations against dedicated programs • include mass shapes and systematic uncertainties a la SM • evaluate discovery poential and exclusion and significance plots for data • and possibility to discriminate SM and SUSY extensions • perform sensitivity studies for yet uncovered regions - need signal efficiency (and shape) in addition • look at new scenarios propsed by our theoretical friends • I do not believe in SUSY, other extensions to SM are also welcome

  39. Final words • newstudiesconfirmgoodsensitivity for discoveryofHiggsbosons • in SM and CP conserving MSSM • CP Violating MSSM and NMSSM needfurtherstudiestoestablish • no lose situation • VBF withHttimportant • - for lowmassHiggsbosondiscovery • - discriminationbtw. SM andextendedsectors • - determinationofspin/CP andmaybemass • Higgssensitivitystarts at > 1fb-1 - due to limited signalrates (except H+-) - requiredgoodunderstandingofdetector • focus for firstdata: - improveandvalidatejetand ETMISS reconstruction (Z+jets) - investigateand tune underlyingevent model (min. biasandZ+jets) - understand backgrounds in phasespace relevant for Higgsbosonsearches

  40. Back up

  41. Discovery = significant deviationfrom SM expectation • significant:probability of background fluctuation <2.9x10-7equivalent to „5 sigmas“ for Gauss distribution • deviation:- new peak in mass distribution - excess in kinematic distribution • for discovery (event counting or more info): - only need knowledge of background - wrong modelling of signal (rate and shape)  non optimal search strategy  more data • for exclusion (and discovery potential) - need signal efficiency (and shape) in addition • determination of background: • (i) from data itself with little theory and MC input • via auxilary measurement from same data set • (ii) prediction from theory + MC + detector performance • background=lumi*cross section*acceptance*efficiency • signal-to-background ratio vs. background uncertainty crucial for discovery significance

  42. Ist es ein Higgs-Boson? Jet 1 V Dfjj V Jet 2 Signal +Untergrund für 10 fb-1 Sensitivität für Ausschluss von CPE/CPO: HWW:~ 5 s mit 10 fb-1 Htt: ~ 2.5 s mit 30 fb-1 (MC-Generator VBFNLO von D. Zeppenfeld et al.) C. Ruwiedel Diplomarbeit BN 2006

  43. Kein Higgs?  Anomale Eichbosonselbstkopllung Verletzt Unitarität bei Energien von ~ 1.2 TeV Restaurierung durch „Neue Physik“ • Untersuchung von ppjj WW jj ln ln Endzustand (VBF-Signatur) • sensitive Observable Azimuthwinkeldifferenz zw. den Leptonen M. Mertens Diplomarbeit BN 2006 Dfll Lept.1 Lept.2 vielversprechende Studie auf dem Weg MC-Generator WHIZARD (W. Kilian, J. Reuter, …)

  44. Hmm: sensitivity Preliminary Preliminary Preliminary Preliminary

  45. MSSM Cross section: Charged Higgs Bosons • light charged boson: production in top decay BR(tH+b) with Feynhiggs 2.6.2 • gbHt: calculated in NLO with program including dominant SUSY loop corrections via Db (taken from Feynhiggs) • decay branching ratios calcluated with Feynhiggs 2.6.2 results in mhmax scenario • production cross sections • decay branching ratios

  46. Charged Higgs boson: search channels • light H+- (MH+- < Mtop) (PYTHIA) Preliminary MH+-= =130GeV tanb=20 • heavy H+- (MH+- >= Mtop) (MATCHIG) Preliminary • backgrounds: tt, single t, W+jets, QCD • top quark production dominant background in all topologies • systematic uncertainties: theo: 15% for tt cross section exp.: 15 to 40% for signal and background (E scale, b-tagging largest)  exctract background from control sample  ~ 10% background uncertainty

  47. Charged Higgs boson sensitivity in mhmax scenario • background uncertainty: 10% • signal uncertainty included for exclusion • limited MC statistics for background also taken into account mhmax scenario mhmax scenario Preliminary Preliminary • most difficult region at intermediate tanb as coupling H+-tb smallest • if statistical uncertainties from limited MC neglected  gap closed

  48. Charged Higgs Bosons high mass: mH+-> mtop gbH+-t H+-tn tbqq low mass: mH+-< mtop ggtt ttH+-bW only low lumi. new: Wqq H+-tn • transition region around mtop needs revised experimental analysis • running bottom quark mass used • Xsec for gbtH+- from T. Plehn‘s program

  49. bbH, Httll 4n Preliminary • only >=1 btag analyis for now • mass resolution ~ 20% • low M: Ztt dominant background larger M: tt dominant BG • background estimate from data a la VBF • uncertainties considered: - exp. uncertainty: 5% signal 8% tt - Z background fom data (several %) - theo. uncertainty for signal: 20%(100 GeV) to 10%(400GeV) • other decays ttl had, had had and 0 btag analysis to come Preliminary

  50. MSSM cross sections: neutral Higgs bosons LH03 hep-ph 0406152 • direct production: calculated with HIGLU • associated production: calculated with Harlander values for NNLO bb->H plus MSSM correction from Feynhiggs 2.6.2 • branching ratios calculated with Feynhiggs 2.6.2 • uncertainties: bbH 10% scales + 14%pdfs (MRST02/04) ggbbH 20-30%

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