Markus Schumacher Klausurtagung Feldberg, Searches for Neutral Higgs Bosons in Supersymmetric Extensions of the SM Motivation Structure of Higgs Sector Theoretical Constraints Status of Searches Prospects for Discovery Standard Model (SM) Minimal Supersymmetric Extension of the SM (MSSM) Next-to-Minimal Supersymmetric Extension of the SM (NMSSM)

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

3 The Brout-Englert-Hagen-Higgs-Kibble-Mechanismus The „Standard“-Solution: doublet of 4 skalar fields with appropiately choosen potential V = -  2 |    | + |    | 2  2, > 0 minimum not at  =0  spontaneous symmetry breaking Higgs field has two components: 1) omnipresent, homogeneous background field v= 247 GeV 2) Higgs-Boson H with unknown mass M H ~  v H restaures unitarity if g HWW ~ M W g Hff ~ M f and M H not too large

4 Mass generation and Higgs boson couplings:  = v + H W/Z Bosonen M V ~ g v gauge coupling Fermions m f ~ g f v Yukawa coupling x x W/Z boson g gauge interaction with v=247 GeV interaction with Higgs-Boson H x W/Z boson g gauge Higgs v 2 2 VVH coupling ~ vev: only exists after electroweak symmetry breaking  observation of VBF yields indirect hint to background field only one free parameter: M H or

5 Theoretical constraints on the Higgs boson mass Unitarity in VV scattering: < 1 TeV energy /temperature dependence of quartic coupling Left diagram: increasing require  < 1 up to energy   upper bound on M H  (M H )v triviality/pertubativity bound Right diagram: decreasing if m t large require  >0 up to energy   lower bound on on M H  (M H )v vacuum stability bound

6 Experimental constraints on M H direct search at LEP: M H < GeV excluded at 95% CL direct search at Tevatron: M H < 154 (185) GeV (incl. dir. limit) indirect prediction in SM: M W (Phys) = M W (Born) + … m t + … ln(M H ) 2 W WW W W H t b M H ~ 170 GeV excluded at 95% CL

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

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

9 VBF:Challenges and our plans reconstruction of taggings jets QCD central jet veto (p t >20 GeV, |  |<3.2) optimise algos and study influence of pile up and underlying event - investigate minimum bias and Z   +jets - use of tracking information mass reco. in collinear approximation  M /M~12to 14% dominated by E miss 20% worse for low lumi. pile-up Preliminary EW

10 Mass distribution and background estimate mass distribution after all cuts peak on shoulder of dominant Z BG  estimate from data needed jjZ   and  jjZ     identical topology 1) select Z   events 2) manipulate  s to look like Z     ll  3) apply standard selection develop similar method for tt background e.g. b-veto vs. b-tag, impact parameter cuts, … Zjj tt Zjj shape from data H

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

12 Exclusion potential 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? Preliminary

13 Stability of the Higgs boson mass without new symmetry: fine tuning to level needed or cut off at 1 TeV the hierarchy problem: why is v=246 GeV <<M planck or M GUT large corrections to Higgs mass divergence cancelled by particle with:  spin = ½, ~ same mass, same coupling if mass correction ~ O(100 GeV)  M SUSY ~O(1TeV)

14 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 Other arguments for SUSY

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

16 SUSY requires 2 Higgs doublets – masses for up and down type fermions - anomaly free  5 Higgs bosons: 3 neutral + 2 charged The MSSM Higgs Sector in the Nutshell scalar potential w/o SUSY breaking „ H 4 " given by gauge couplings, no EW-symmetry breaking different m 1, m 2 evolution  m 2 negative  triggers EW-symmetry breaking after EWSB: two free parameters in Higgs sector (v 1 + v 2 = v SM ) scalar potenital after SUSY breaking 222

17 at Born level: - 2 parameters: tan  v 2 /v 1 and M A - CP conserved  2 neutral CP-even h,H + 1 CP-odd A - upper mass bound (quartic coupling = gauge couplings): M h < M Z The MSSM Higgs Sector in the Nutshell m h < 133 GeV (+-3GeV) for m top =175 GeV, M SUSY =1TeV in constrained MSSM a la LEP/LHC corrections depend on 5 SUSY parameters: X t mixing in stop sector M 0 common sfermion mass at EW scale M 2, SU(2) gaugino mass at EW scale, M1 from GUT relation M gluino gluino mass  Higgs mass mixing parameter 5 parameters fixed in the benchmark scenarios considered large loop corrections from SUSY breaking sector esp. top/stop mSUGRA: X t, M 0 for Higgs and sfermion, M 1/2 for gauginos, sign , tan 

18 MSSM Higgs Bosons Phenomenologie new production mode: b(b)Higgs modified couplings g MSSM =  g SM  t b/ W/Z h cossin-sincossin() H sinsincos/coscos() A cottan  = mixing btw. CP-even neutral Higgs bosons  no coupling of A to W/Z  small    small BR(h  ,bb)  large    large BR(h,H,A  ,bb) Higgs boson mass pattern

19 Constraints on the Higgs sector EW precision data, dark matter density, a , b  s  in CMSSM = mSUGRA MSSM bounds precision from DM, a , b  s  constraints Constrained MSSM: M h <133 GeV for m top =175 GeV, M SUSY =1TeV General MSSM: M h <150GeV

20 Constraints on the Higgs sector: direct searches TEVATRON: largest sensitivity at large tan   via bbH  H   LEP: investigated 5+3 benchmarks M h/A <~ M Z excluded at 95% CL

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) Gluophobic scenario small g h,gluon m h < 119 GeV Small a scenario small g hbb and g htt m h <123 GeV MHMAX scenario maximal m h < 133 GeV  conservative LEP exclusion Nomixing scenario small m h < 116 GeV  difficult for LHC 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) 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 ! M t = 175 GeV

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

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

25 Light Higgs Boson h: 30 fb -1 difference mainly due to different m h in same (tan ,M A ) point ( up to 17 GeV difference) observable channels: VBF bbh h   (tth h  bb w/o syst. error) Preliminary

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

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

28 Heavy Neutral Higgs Bosons  ~ (tan  ) 2 old LO study:   lep had +  had had (M > 450 GeV) most promising: bbH/A, H/A   Preliminary new NLO study:   lep lep same BGs as VBF, H   mass reco. and BG estimate a la VBF no forward jet and CJV but b-tag instead of b-veto Preliminary ATLAS preliminary

29 Overall discovery potential in CP conserving MSSM 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? similar results in other benchmark scenarios VBF channels, H/A   only used with 30fb fb -1 ATLAS preliminary Preliminary

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

31 The CP violating complex MSSM A t, A b M gluino „new“ Born level pars: tan  and M H+- mass eigenstates H 1, H 2, H 3 not equal CP eigenstates h,A,H MSSM Higgs sector CP conserving at Born level CP effects via complex couplings in loops 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 m stop <m top and M H1 <120 GeV

32 Phenomenology in the CPX scenario H 1,H 2, H 3 couple to W,Z H3 H2 H1 H 2,H 3  H 1 H 1, ZH 1, WW, ZZ decays sum rule:  i g i (ZZH i ) = g SM no absolute limit on mass of H 1 from LEP strong dependence of excluded region on value for m top on calculation used FeynHiggs vs CPH

33 Discovery potential in CP violating MSSM yet uncovered region in parameter space for light Higgs boson (not yet studied) promising channels: tt  bbH + W -  bbH 1 W + W -  bbbbl qq Higgs in SUSY cascades,…. 300 fb -1 CPX scenario (Carena et al., Phys.Lett B (2000)) arg(A t )=arg(A b )=arg(M gluino )=90 o,,M SUSY = 500 GeV, A t =A b =M gluino =1 TeV, m=2TeV, M 2 =200GeV

34 The  -problem MSSM Superpotential  : the only parameter with mass dimension bevor SUSY breaking  not protected by symmetry, could be M GUT but correct EWSB requires O(.1 to 1 TeV) idea: replace  by condensate of new scalar complex singlet field S which is only coupled to MSSM Higgs fields seven Higgs bosons: 3 CP-even, 2-CP-odd, 2 charged 5th neutralino from superpartner of S several variants on the market: NMSSM, MNMSSM,… and also not SUSY singlet extensions 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 ) (more benchmarks in PhD thesis by I. Rottländer, CERN-THESIS ) 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 M H1 ~ 120 GeV and SM-like M H2 ~ heavy and decoupled in unexcluded region M A1 < M H1 /2 in almost whole plane BR(H 1  A 1 A 1 ) BR(A 1   ) H 3,A 2,H +- too heavy

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

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 new studies confirm good sensitivity for discovery of Higgs bosons in SM and CP conserving MSSM CP Violating MSSM and NMSSM need further studies to establish no lose situation VBF with H   important - for low mass Higgs boson discovery - discrimination btw. SM and extended sectors - determination of spin/CP and maybe mass Higgs sensitivity starts at > 1fb -1 - due to limited signal rates (except H +- ) - required good understanding of detector focus for first data: - improve and validate jet and ETMISS reconstruction (Z+jets) - investigate and tune underlying event model (min. bias and Z+jets) - understand backgrounds in phase space relevant for Higgs boson searches

40 Back up

41 Discovery = significant deviation from SM expectation significant: probability of background fluctuation <2.9x10 -7 equivalent 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? Signal +Untergrund für 10 fb -1 Sensitivität für Ausschluss von CPE/CPO: H  WW: ~ 5  mit 10 fb -1 H   : ~ 2.5  mit 30 fb -1 (MC-Generator VBFNLO von D. Zeppenfeld et al.) C. Ruwiedel Diplomarbeit BN 2006  jj Jet 1 Jet 2 V V

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

44 H   : sensitivity Preliminary

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

46 Charged Higgs boson: search channels 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 Preliminary light H+- (M H+- < M top ) (PYTHIA) heavy H+- (M H+- >= M top ) (MATCHIG) M H+-= =130GeV tan  =20 backgrounds: tt, single t, W+jets, QCD

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 most difficult region at intermediate tan  as coupling H +- tb smallest if statistical uncertainties from limited MC neglected  gap closed Preliminary mhmax scenario

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

49 bbH, H    ll 4 only >=1 btag analyis for now mass resolution ~ 20% low M: Z   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   l had, had had and 0 btag analysis to come Preliminary

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

51 Light Higgs Boson H 1  border of discovery region at low tanb mostly determined by availability of inputs (VBF >110 GeV, ttH and  > 70 GeV)  border at low M H+- due to decoupling of H 1 from W,Z and t 30 fb fb -1 ATLAS preliminary  for VBF channels: assume same efficiencies for contribution of CP even and CP odd states (needs to be checked)  for ttH: efficiencies for CP even and odd bosons are the same