Search for the Higgs bosons in supersymmetric extensions of the SM

1. Search for the Higgs bosons in supersymmetric extensions of the SM Giorgos Dedes Seminar : Physik am Large Hadron Collider (LHC)

2. Outlook • ATLAS - CMS • SUSY – MSSM Higgs sector • Higgs masses • Production and Decay • Benchmark scenarios • Higgs searches • Summary

3. ATLAS • Inner Detector:Highly segmentedsilicon strips, determine very accurately charged particles trajectories • Solenoid Magnet: Solenoid coil that generates a 2T magnetic field in the region of the Inner Detector • Electromagnetic Calorimeter: Electron and photon energies are measured through electromagnetic showers • Hadronic Calorimeter: Hadrons interact with dense material and produce a shower of charged particles • Toroid Magnets: 8 toroidal coils that create a 0,4T magnetic field in the area of the Muon Spectrometer • Muon Spectrometer:Muons traverse the rest of the detector and are measured in its outer layers

4. CMS • Tracker:Cocentric layers ofsilicon sensors, measure charged particles trajectories • Electromagnetic Calorimeter: Lead-Tungstate crystals, electrons – positrons – photons interact there and their energy is measured • Hadronic Calorimeter: Hadrons interact brass layers and produce a shower of charged particles • Solenoid Magnet: Largest solenoid ever built, creates 4T field that bends the charged particle trajectories • Return Yoke:Magnetic field created from the solenoid is returned in the iron yoke. Offers support structure for the detector • Muon Chambers:Located in the iron yoke, measure energy of muons

5. SuperSymmetry (motivation from Higgs sector) • Hierarchy problem in the SM Higgs sector: Quantum corrections to the H mass have quadratic divergencies • By introducing supersymmetric partners for the SM particles • quadratic divergencies are cancelled

6. SuperSymmetry • By introducing superparticles, the SM particle spectrum is doubled.

7. MSSM (in a nutshell) • MSSM is the minimal extension to the standard model that realizes supersymmetry. • It imposes an extra symmetry, R parity • Sparticles enter interactions in pairs, with particles having R parity of 1 and sparticles of -1 • Sparticles are produced and annihilated in pairs

8. 3 are absorbed from the H mechanism and give masses to W± and Z 5 physical Higgs bosons 8 degrees of freedom MSSM Higgs sector • In order to implement electroweak symmetry breaking into the MSSM, two Higgs doublets (H1, H2) that couple to up and down type particles, are needed. • 2 CP even (h, H),1 CP odd (A) and 2 charged H± • The MSSM Higgs sector (at tree level) is determined by 2 free parameters MAand tanβ=v2/v1(ratio of the vacuum expectation values of the 2 Higgs doublets) • In CP conserving scenarios mass eigenstates are equal to CP eigenstates. In CP violating scenarios additional free parameters appear. Non vanishing phases mix the CP eigenstates to 3 mass eigenstates

9. Higgs masses • At tree level: andfor This gives us an upper limit for the h mass • Modifications to tree level due to top loops give additional contributions to Mh So Mh < 133 GeV • For the decoupling limit MA>>MZ A and H have similar couplings and are degenerate in mass while h resembles standard model Higgs

10. Higgs production (neutral) • d • Main production mechanisms: gluon fusion and associated production with b-quarks which is dominant at high values of tanβ • Vector boson fusion and Higgs-strahlung are suppressed for h/H/A (suppressed coupling to W±, Z) • With respect to the SM, cross sections are enhanced with rising tanβ

11. Higgs production (charged) • Three main production processes in LHC, for single H± • From tt via gg fusion • In association with top and b quarks • In association with t quark

12. Higgs decays • For large tanβ, the dominant decay channels for h/H/A are bb and ττ • H± branching ratios are divided to 2 regions: dominant decay to τν for MH± <Mt and decay to tb for MH± >Mt

13. Benchmark scenarios • Due to the large number of free parameters, the MSSM Higgs search is performed in 4 CP conserving (CPC) and 1 CP violating (CPV) scenarios • CPC scenarios: • mh – max scenario (MSUSY = 1TeV, μ=200GeV, M2=200GeV, Xt=√6MSUSY, Ab=At, Mgluino=0,8MSUSY) • no - mixing scenario (MSUSY = 2TeV, μ=200GeV, M2=200GeV, Xt=0, Ab=At, Mgluino=0,8MSUSY) • gluophobic scenario (MSUSY = 350GeV, μ=300GeV, M2=300GeV, Xt=-750GeV, Ab=At, Mgluino=500GeV) • small α scenario (MSUSY = 800GeV, μ=2TeV, M2=500GeV, Xt=-1100GeV, Ab=At, Mgluino=500GeV) • CPV scenario: the CPX scenario (MSUSY = 500GeV, μ=2TeV, M2=200GeV, Ab=At, Mgluino=1000GeV)

14. Benchmark scenarios • mh-max scenario:Designed to maximize the h mass. Gives a limit for the Mh (133 GeV) that strongly depends on Mt • no-mixing scenario:Similar to mh-max but with no mixing in the stop sector. Designed to explore the effect of no stop mixing, results to Mh < 116 GeV (Difficult for LHC) • gluophobic scenario:Coupling of h to gluons strongly suppressed. Designed to affect the processes gg→h , h→γγ and h→ZZ →4l. Yields a Mh < 119 GeV • small α scenario:Coupling of h to b and τ is suppressed. Mh < 123 GeV. Designed to affect the channels h→ττ and tth, h→bb • CPX scenario: CP eigenstates do not coincide with mass eigenstates. So h, A, H mix to mass eigenstates H1, H2, H3. CPX has maximal mixing (90 degrees) Suppressed h-gluon coupling

15. Status of previous Higgs searches • The search for MSSM H bosons has been performed at LEP and is an ongoing effort at Tevatron • LEP: 8 scenarios scanned at LEP1 and LEP2 No discovery but limits for the masses and tanβ have been set. tanβ exclusion 0,7 – 2.0 and Mh , MA > 90 GeV • Tevatron: Still no discovery, a large part of the tanβ - MA parameter space will be covered with 5 fb-1 of data (2007-2008)

16. Higgs searches in LHC • ATLAS and CMS will cover a large variety of different final states and a big part of the (MA, tanβ) plane • The channels investigated during the last years in ATLAS and CMS are: h/H/A→γγ h/H/A→bb h/H/A→ττ h/H/A→μμ H→ZZ , tt , hh A→Zh H±→τν , tb H/A→χo2χo2

17. h / H / A → γγ • The expected MSSM rates for h and H decaying to γγ are generally suppressed with respect to SM case. For this rare decay, A boson is only observable in a limited region of the parameter space. • Optimistic scenario: Branching ratio is estimated assuming that all SUSY particles have a mass higher than 1TeV (there can be stop-quarks , charginos and neutralinos lighter than 1TeV) • The same kinematic cuts are applied as in the case of the SM 2 photon candidates ordered in PT (starting from PT1 > 40GeV and PT2 > 25GeV for h and reaching PT1 > 125GeV and PT2 > 25GeV for the heavy Higgses • Both photon candidates in |n|<2,4 and events with more than one γ in transition region in an interval Δn = 0,15 are rejected • Backgrounds: γγpair production, γ-jet, dijet and Z→ee ATLAS

18. h / H / A → bb ATLAS • More promising channel is h / H / A → bb , due to the high branching ratio (~90%) especially for high values of tanβ • For the low mass Higgs best sensitivity is achieved in the tth, h→bb • For high mass region bbH/A, H/A→bb • Quite challenging to trigger a 4 jet final state • Require 2 hard jets from Higgs decay and 2 softer tagging jets • Enormous QCD background • Complex final state, 20% combinatoric background ATLAS

19. h / H / A → bb • In more recent study performed for the CMS detector, this channel is considered as cross check after discovery in H / A → ττ CMS • At least 4 jets are required within the detector acceptance |n|<2,4 with the hardest 2 passing PT thresholds dependant on the Higgs mass • Additional selection in CMS analysis the centrality variable • Discovery possible for tanβ>30 (largely dependant on background uncertainties) CMS

20. h / H / A → ττ • For h main production mechanism is VBF while for H/A associated production with b-jets • All τ decay modes have been considered (lepton-lepton / lepton – hadron / hadron - hadron) • Due to the escaping neutrinos mass reconstructions is done by using the collinear approximation ATLAS • Mass resolution dependant on Δφ between the visible decay products and sensitive to ETmiss resolution

21. h / H / A → ττ • Is considered a discovery channel for heavy neutral Higgs, especially in mass range 150 – 300 GeV

22. h / H / A → μμ ATLAS • Same coupling as for ττ channel, but BR scales as (mμ/mτ)2 ≈ 1/300 • For high tanβ, associated production with b-jets is dominant • Clean signature in the detector • Excellent mass resolution, can provide the best mass and width measurement for H/A

23. H→ZZ(*) →4l , H→tt • h/H→ZZ(*): Not thoroughly searched, extrapolated results from SM For high tanβ suppressed HZZ coupling, rise of hh tt If observed identified from the low rate ATLAS MH=370GeV tanβ=1,5 • H→tt: Suppressed coupling with gauge bosons, tt becomes interesting Observed as peak over the continuous tt background Mass reconstruction from the decay channel bWbW→blνbj

24. H→hh , A→Zh • Would allow simultaneous observation of 2 Higgs bosons • For H→hh, possible decays are: bbbb (largest rate-difficult trigger), bbττ(can trigger on leptonic tau), bbγγ(easy to trigger – low rate) • For A→Zh with final state: μμbb or eebb , require 2 leptons with Z mass constrain and 2 bjets well separated from the leptons Signal Zbb tt Z+jets

25. H±→ τν / tb • 2 prominent decay modes, τν / tb for MH lower/higher than tb production threshold • MH < Mt : tt→H±Wbb→(τν)(lν)bb→(hνν)(lν)bb , trigger from W leptonic decay • MH > Mt : gg→tbH± →(bW)b(τν)→(bjj)b(hνν) , disentangle τ-jet from light jets t mass constraint tb decay channel opens gg→tbH± →tb(tb)→WWbbbb→qqμνbbbb gb→tH± →t(tb)→WWbbb→qqμνbbb has large tt+jets background , multivariate techniques used CMS , 30fb-1 3-tags

26. A/H →χo2χo2 • MSSM Higgs can be also searched in decays to supersymmetric particles • Can give us a handle on the low and intermediate tanβ region not accessible by A/H→ττ • Promising decay into the next to lightest neutralinos , χo2→l+l-χo1 • Main backgrounds: squarks and gluinos cascade decays , ZZ(*), Zbb • Apply lepton isolation , jet andZ veto • No mass peak reconstruction, excess of events

27. Overall discovery potential • In LHCMSSM Higgs could be discovered within the first years (30 fb-1) • At 300 fb-1, the biggest part of the parameter space will have been scaned • A challenge for both theorists and experimentals : A region where only one Higgs can be seen, is it SM or MSSM ?

28. Conclusions • Supersymmetry and MSSM in particular are favorite candidates for extension of the SM • Searches for the MSSM Higgs have been started at LEP, continue at Tevatron and will start soon in LHC experiments • A large number of processes provide us the capability to scan a large area of the parameter space • Tevatron could surprise us, otherwise LHC can give as indications during the first 3 years and discovery afterwards

29. Backup slides

30. Production cs at low tanb

31. A BR also in SUSY particles

32. MSSM Higgs sector

33. h/H/A couplings

34. CPV mixing

35. SM – MSSM discrimination

36. Other contributions in cs

37. h discovery potential • ….dependence on scenarios…

39. CPV discovery potential