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Exploring Higgs Boson Models at LEP Moriond 2004

Detailed exploration of Higgs boson searches using data from LEP collider, covering Standard Model Higgs, MSSM, 2HDM, and more. Exclusions, benchmarks, and impact of top mass on findings are discussed.

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Exploring Higgs Boson Models at LEP Moriond 2004

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  1. Searches at LEP Moriond Electroweak 2004 Ivo van Vulpen CERN On behalf of the LEP collaborations

  2. USY searches iggs searches LEP and the LEP data LEP: e+e- collider ats  mZ (LEP1) and s = 130-209 GeV (LEP2) Most results (95% CL limits) based on LEP2: Int. Lum.  2.6 fb-1 4 experiments: Aleph, Delphi, Opal and L3 Outline of the talk e otica Ivo van Vulpen

  3. Higgs Searches Higgs Searches http://lephiggs.web.cern.ch/LEPHIGGS/www/Welcome.html Ivo van Vulpen

  4. Higgs Searches Higgs Searches covered in this talk  SM Higgs boson  General 2HDM MSSM (CP-conserving)  3 benchmarks  Flavour independent  Charged Higgs boson MSSM (CP non-conserving)  Fermiophobic  Invisible Higgs boson  Not covered: MSSM Gluophobic (LHC), Double charged Higgs bosons, Anomalous Higgs couplings, Yukawa Higgs production, Extended Models, many many more …… Ivo van Vulpen

  5. Higgs Searches SM Higgs boson Higgs strahlung h In the SM we know everything about the Higgs boson (except its mass) mh > 115.3 GeV (expected)  mh > 114.4 GeV (observed) Weak boson fusion Excess at 115 GeV: -2ln(Q) at mh = 115 GeV Exclusion on HZZ coupling 100,000 signal+background experiments (MC) 100,000 background-only experiments (MC) LEP data Ivo van Vulpen

  6. Higgs Searches h h A Two Higgs Doublet Models (2HDM) Simplest extension of the SM: Add 2 complex Higgs Doublets (H1, H2) Parameters:tan() (=v1/v2),  (=mixing h0,H0) + Higgs boson masses Higgses:2 CP-even: h0, H0 Models:2HDM(I): One doublet for all fermions 1 CP-odd: A0 2HDM(II): One up-type doublet MSSM 2 charged: H+,H- One down-type doublet Neutral Higgs boson production: Higgs boson decay: Depends on model parameters couples to mass, so mainly: Higgs strahlung Associated production Ivo van Vulpen

  7. Higgs Searches Higgs Searches 3) large- (H in reach, but regions with reduced bb couplings) MSSM 7 parameters Tree-level parameters tan() Higgs vev ratio mA Mass of CP-odd Higgs Three benchmark scenarios: 1) mh-max (max mh for each tan()) Loop-level parameters 2) no-mixing (in the stop sector) A Trilinear Higgs-sfermion coupling mgMass of the gluino Higgs mass parameter msusy Sfermion mass at EW scale M2 Gaugino mass at EW scale Xt = stop mixing = At - cot() Ivo van Vulpen

  8. Higgs Searches Higgs Searches Flavour independent Higgs bosons  Reduced couplings to bb DELPHI hA -> hadrons (preliminary) mS2 100% mh > 113.0 GeV (expected) Model independent mh > 112.9 GeV (observed) 10% hA hZ mS1 unexcluded Mass exclusion usingSM(hZ): 2.3 GeV worse than SM Higgs  Adding flavour independent  OPAL also made a decay mode independent search excludes large- scenario MSSM benchmark (large )  Lightest Higgs: mh < 108 GeV Higgs decays to cc or gluons LEP combined: 88-209 GeV Ivo van Vulpen

  9. Higgs Searches Higgs Searches hA hZ Scenario mh mA Excluded tan() Mh-max>91.0 >91.90.5 < tan() < 2.4 No mixing >91.5 >92.2 0.7 < tan() < 10.5 Mh-max MSSM benchmarks No-mixing hZsmall hAkinem. out of reach Mh>2mA: h->AA dominant Extend searches for h->AA (mA<mb) and H+ conservative tan() exclusion depends strongly on the top mass Ivo van Vulpen

  10. Influence of the top mass on tan() exclusion region: In MSSM benchmarks: mtop = 175 GeV Maximum mh: in the MSSM 135 GeV ~ Computation of mh-max: Loop corrections m4top FeynHiggs: higher order corr. -> mh  3 GeV mh-max benchmark scenario mtop  5 GeV -> mh  5 GeV mh If mtop is larger than 175 GeV, the LEP-excluded tan() region shrinks Depends on results from CDF & D0 --> K. Bloom & Y.Kulik (this session) Ivo van Vulpen

  11. Higgs Searches Higgs Searches A ˜ ˜ Different CP-phase t,b h,H H1 Note: only h,H (CP-even) couple to Z. MSSM CP non-conserving scenarios  Break CP symmetry by radiative corrections Low mass regions open up CP conserved:(H1, H2) -> mass eigenstates are CP-eigenstates tan() versus mH1 h,H (CP-even), A (CP-odd) e+e- -> hZ and e+e- -> hA CP: H1, H2 H3 are mass-, but not CP-eigenstates A tan() M2 m4top Im (,At) / v2 m2susy OPAL CP benchmark: CPXScan parameters: tan() andmH+ mH1 (Msusy = 500 GeV, =4 Msusy, |At,b|=|mg|=2 Msusy) Ivo van Vulpen

  12. Higgs Searches  h Z Roughly 100 times SM prediction WW  ZZ* 100 GeV Fermiophobic Higgs bosons  In 2HDM (I) models Higgs couplings to fermions can be close to 0  Decays to photons (W-loop) is dominant mh > 109.7 GeV (observed) Ivo van Vulpen

  13. Higgs Searches h Mh > 113.5 GeV (exp.) Mh > 114.4 GeV (obs.) Invisible Higgs bosons  MSSM: Higgs boson might decay into Expected Cross section LEP combined stable Excluded Cross section Ivo van Vulpen

  14. MSSM (h) 91.0 GeV MSSM (A) 91.9 GeV Higgs boson summary: Observed Lower limit on mh (GeV) Higgs scenario SM Higgs 114.4 GeV Flavour independent 112.9 GeV Charged Higgs bosons 78.6 GeV Fermiophobic 109.7 GeV Invisible 114.4 GeV Ivo van Vulpen

  15. SuperSymmetry http://lepsusy.web.cern.ch/lepsusy/ Ivo van Vulpen

  16. SUSY Searches SUSY model covered in this talk R-parity conservation there is a stable Lightest Supersymmetric Particle (LSP) SUSY particles are produced in pairs Mass universality at the GUT scale sfermions (m0) cMSSM gauginos (m1/2) 8 parameters: m1/2, m0, tan(), , mA and Af(At, Ab,A) SUSY broken by gravitation (SUGRA): Signature: Missing energy (escaping neutralino) and dependence on M (msparticle- mLSP) This talk:Results on sleptons, squarks, charginos --> lower limit on the mass of the LSP Last slide:Results on R-parity violation, GMSB. Ivo van Vulpen

  17. SUSY Searches e e+ Z/ e- e sleptons production M small e cross sections for lR smaller than lL decay M  = -200 GeV and tan() = 1.5 very soft leptons Mass limits: Lower limits in GeV = 0 GeV99.6 94.9 85.9 85.0 from the Z = 40 GeV99.4 96.5 92.5 91.7 Ivo van Vulpen

  18. SUSY Searches sbottom stop e+ Z/ e- sbottom Signature: acoplanar jets + E and P M< mc: squark is a quasi-stable particle Mass limit 100 (98) 99 (96) 99 (95) (main)decays production: squarks stop Mixing in 3rd family: Mass limits (in GeV): M = 20 GeV & for (non)-decoupled from Z Ivo van Vulpen

  19. SUSY Searches new A light sbottom Excess in bb cross section at the Tevatron: How abouta12-16 GeV gluino and 2-5.5 GeV sbottom ?? P.Janot hep-ph/0403157  Moriond 2003: (ALEPH) Stable sbottoms: Msbottom> 92 GeV  Hadronic cross section data from: 95% CL lower limit on msbottom (GeV) LEP1, LEP2 and PEP, PETRA, TRISTAN, Small coupling sbottom to Z The older generations in the LEPfamily help out (use s = 20-209 GeV) Hadronically decaying sbottom: Msbottom > 6.0 GeV cos mix Ivo van Vulpen

  20. e+ Z/ e+  e- W+ e- l+ Small m0: light sfermions Charginos: large m0 Large cross section in large part of parameter space production decay Negative interference if chargino is gaugino W-> qq (68%) / lv (32%) 1) M > 3 GeV: LEP combined 2) 200 MeV < M < 3 GeV: low momentum particles (use ISR -> high PT-) 3) M < 200 MeV: ‘kinky’ tracks and displaced vertices Long lived charged particles (dE/dx information) Ivo van Vulpen

  21. SUSY Searches  The LSP cMSSM Interpret the combined results in the cMSSM framework Combining results from Higgs searches with slepton, chargino and neutralino searches Use cMSSM mass relations m0 large m0 small Assuming m0 < 1 TeV and mtop = 175 GeV and no stau mixing Ivo van Vulpen

  22. SUSY Searches  Assuming m0 < 1TeV A 0 0 any sign() mtop 175 180 175 positive 59.0 53.9 50.8 negative58.6 52.0 50.3 The LSP mSUGRA Interpret the combined results in the mSUGRA framework MSUGRA = cMSSM +1) common scalar mass (mA via m0) +2) common trilinear coupling at GUT (At, Ab,A = A) +3) fix || (EW symmetry breaking) ( -> sign()) 5 parameters: m1/2, m0, tan(), sign(), A A=0, mtop = 175 GeV A=0, mtop = 180 GeV Any A mtop = 175 GeV Ivo van Vulpen

  23. SUSY summary:  Not shown: AMSB & scenarios where the sneutrino or the gluino is the LSP Ivo van Vulpen

  24. Exotica Searches Low scale gravity in Extra dimensions Gravity strong near the EW scale Data/MC n extra (space) dimensions of radius r Virtual graviton exchange affects: Put limits on MH (gravitational mass scale): MH> 1.20 TeV (= +1) cos(e) MH> 1.09 TeV (= -1)  Not shown: technicolour, single top, leptoquarks, excited fermions, Z’, cont. interactions, 4th generation quarks … Ivo van Vulpen

  25. Conclusions: SM Higgs combined and published Searches for SUSY Higgs bosons -> exclude large part of MSSM parameter space Final benchmark scans this summer (also gluophobic – interesting for LHC)  LEP combined searches for sparticles Interpretations in a wide variety of SUSY models Rest of the cheese is for the Tevatron & LHC Ivo van Vulpen

  26. Backup slides Ivo van Vulpen

  27. Higgs Searches Hypotheses testing: Likelihood ratio method  Construct 2-dim distr. for background(mh) and signal(mh)+background --> (Mhrec, ) Higgs mass estimator  For each event i-> you know wi = P(s+b)/P(b) separating variable  Define test-statistic as –2ln(Q), with Q = Ls+b / Lb (=i wi) with weights Number of expected signal events Ratio of the expected number of signal events over the expected number of signal events in a locql bin of (Mhrec, ) Number of selected candidates 100,000 signal+background experiments (MC) 100,000 background-only experiments (MC) The rules: LEP 1-Clb: incompatibility with the background-only hypothesis 1-Clb < 2.7 10-3 --> 3 sigma 1-Clb < 5.7 10-7 --> Nobel Prize ! CLs+b: compatibility with the signal+background hypothesis 1-Clb Cls+b CLs: compatibility with a signal hypothesis. CLs CLs+b/CLb Cls < 0.05--> Signal hypoth. excluded ‘at 95% CL’ Ivo van Vulpen

  28. Higgs Searches Analysis: only for mA>12 GeV (bb) Mh > 78.8 GeV (exp.) Mh > 78.6 GeV (obs.) Charged Higgs bosons  Assumption of fermion decay is not valid in unexcluded 2HDM(II) no-mixing point Br(H+-> AW+*) can be 60% mA < 12 GeV --> special effort Extended h->AA reach (A->cc/+-/gluons) BR(H--> ) WW background OPAL Excluded Excluded LEP1 Excluded But … unfortunately Included in next (final?) benchmark scan Ivo van Vulpen

  29. SUSY Searches  e+ Z e+ Z e- e- Neutralinos • neutralino decay neutralino production Z-> qq (70%) / v v (20%) / ll(10%) Positive interference if neutralino is gaugino  Phenomenology depends onM, but also on m0 (common sfermion mass at GUT scale) Ivo van Vulpen

  30. Exotica  Excited leptons: Fermion sub-structure: (compositness scale in TeV region) Excluded Decay: l* -> l / lZ / W * * More sensitive due to t-channel - exchange e*  Not covered: technicolor, single top, leptoquarks, extra dimensions, etc… Ivo van Vulpen

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