Searches for MSSM Higgs at the Tevatron

1
Searches for MSSM Higgs at the Tevatron
Amy Connolly/ UC Berkeley For the CDF and DØ
Collaborations

• Motivation
• A/H-gttt
• Run I Run II (CDF)
• A/Hbb -gt bbbb
• Run 1 Search CDF
• Run II
• CDF
• DØ
• Conclusions

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Why Higgs? Why MSSM?

• an EWSB mechanism in SM
• Gives mass to particles through H couplings
• Current data points to light Higgs
• MHiggs lt 170 GeV _at_ 95, Osaka00
• Higgs has not been definitively observed
• LEP2 gt 114 GeV 95 CL exclusion
• a solution to hierarchy problem
• mH2 receives corrections mPlanck2
• Needs fine-tuned parameters for mH100 GeV
• Supersymmetry symmetry between fermions, bosons
  -gt cancellations occur naturally
• Two Higgs doublets are needed

3
MSSM Higgs

• In the MSSM scenario
• Two Higgs doublets lead to 5 Higgs particles
• Two neutral CP-even h,H
• One neutral CP-odd A
• Two charged H ,H-
• Masses governed by two parameters, for ex
• Tree level mass relations
• M(h)ltM(Z)ltM(H)
• M(A) ltM(H)
• M(H)ltM(W)
• M(ho)lt130 GeV after radiative corrections
  (top,stop etc.)

mA-mh
mH-mA
mA (GeV)
mA (GeV)

• High tanb
• A nearly degenerate with
• h (mAlt130 GeV)
• or H (mAgt130 GeV)

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MSSM Higgs production _at_ Tevatron

• H/h/A can have SM-like x-sections at small tan b
• For processes such as HW and HZ

• Some production processes such as
• gg-gtA/H
• gg,qq-gt Hbb/hbb/Abb
• can have
• large x-sections at
• large tan b !!!

Mh/H (GeV)
MA (GeV)
g 1/cosb tanb
? h,H,A
Mh/H (GeV)
MA (GeV)
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MSSM Higgs Branching Ratios
tan b 50
In the same high tanb region, BR(-gtfermions)
stays high even at large mass.
For all practical purposes ??bb 90 ??tt
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mA (GeV)

• Searches for Higgs in high tanb region at
  Tevatron
• gg-gtA/h-gttt
• gg,qq-gtA/hbb-gtbbbb

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A/H-gtttTau ID in Run I (CDF)

• Tau Properties
• Collimated decay products
• Opening angle
• q lt mt/ET(t) lt 0.2 rad 10
• Low multiplicity tracks, photons in 10
• Visible energy reconstructs low mass
• Cuts
• Jet with high visible ET containing high pT track
• Isolated in 10-30 annulus
• Low track, photon multiplicity in 10 cone
• mtlt1.8 GeV
• Q1

Achieved fake rates 1.2-0.7 for jet ET 20-200
GeV
Photons detected in wire chambers at shower-max
in the EM Calorimeter 2D info, s(x),s(z)2cm
Jet ET (GeV)
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A/H-gtttDitau Mass Reconstruction (CDF)

• Full mass of the ditau system may be
  reconstructed if
• Assume ns in same direction as visible decay
  products
• Taus are not back-to-back in azimuthal
• -gtrequire Dflt160

Exmeas Ext1 Ext2 Eymeas Eyt1 Eyt2
Simulation
Simulation
mA95 GeV mean93.7 RMS24.1
Require En1,2gt0 ? Lose 50 Higgs signal, Reject
97 Wjets
Et1
Ditau Mass (GeV)
Et2
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A/H-gttt (CDF)

• Trigger
• No t trigger in Run I ? use pTgt18 GeV lepton
  trigger-gt
• Backgrounds
• Z ? tt (irred.), QCD, Z ? ee, Wjets non-irred.
  backgrounds rejected through tau ID cuts and mass
  reconstruction

One leptonic t One hadronic t
Use mA95 GeV, tanb40 as benchmark s(A/H ?
tt)8.7pb
Z-gttt A-gttt

• Z ? tt irred. backgnd, but
• Branching Ratio
• Z?tt 3.7
• A/H ? tt 9
• PT Distributions
• Stiffer A/H pT distributions than Z pT
  distributions
• Dflt160 cut pTgt15 GeV cut ?
• 30 more efficient for Higgs than Z

pT (GeV)
s(A/H) falls fast! Drops by factor of 4 from 95
120 GeV, 1 RMS (mtt) 24 GeV -gt Need as high a
rate as possible! -gt
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Taus in Run II (CDF,DØ)

• Triggers designed for t physics will greatly
  increase the acceptance for this search
• Lower pT thresholds
• All-hadronic modes open up (1/2 of branching
  ratio)
• Tau Triggers in Run II
• Lepton track triggers (DØ, CDF)
• tMET Trigger (DØ,CDF)
• 2 hadronic ts
• Calorimeter-based (CDF)
• Track-based (DØ)

CDF already sees W?tn events from new tMET
trigger!
Run I A/H-gttt search sill work in progress, Run
II analysis in the works as well
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pp -gt bbA/h/H -gt bbbb Run I (CDF)
? h,H,A
tanb

• Event selection
• 4- jets ?ETgt125 GeV trigger
• ? 3 b-tag (displaced vertex)
• ??bb gt 1.9
• mj dependent cuts optimized for max. expected
  signif.
• gt ET cuts on jets
• gt mass window 1-3s
• BR x Accept 0.2 0.6 (70ltmjlt300 GeV)

mA (GeV/c2)
Backgrounds QCD, Z/Wjets,tt

• For mj 70 GeV hypothesis, observe
• 5 events, expect 4.6 1.4
• Only these 5 events appear in higher mass
  windows
• No excess above predicted is
  observed

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Tools for pp -gt A/h/Hbb -gt bbbb Run II (CDF)
Simulation
Dijet Invariant Mass (GeV)
Dijet Invariant Mass (GeV)

• Z-gtbb studies -gt improved resolution
• - correcting for m, ET, jet charged fraction
• Studies of QCD jets
• - 30 improvement in jet res.
• - uses tracking, shower-max detectors and
  calorimetry

• B-tagging
• 3D silicon
• ? lt 2
• Improved lepton acceptance
• New specific triggers to recover acceptance
  (displaced track trigger, multijet)

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Tools for pp -gt A/h/Hbb -gt bbbb Run II (DØ)
Simulation

• Obtain fractional resolution s/M 12
• No jet calibration applied
• Consider all jet permutations for mass
  reconstruction
• Predicted rates normalized to SM prediction (3.7
  fb)
• Started recently to look at gb?bh channel which
  has an order of magnitude larger cross section

• Multijet trigger 4 jets, ETgt15 GeV, hlt2
• Leading jets mj dependent cuts
• mj120 ET1gt55 GeV, ET2gt40 GeV
• SET of jets 3 and 4 gt 30 GeV
• At least 3 b tags
• plot all mass combinations, look in mass window

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Projected Reach in Run II(CDF, DØ)

• Both experiments study expected Run II
  sensitivity from bbbb analysis
• similar results

2fb-1 -gt160 GeV (tanb40) 95 CL -gt115
GeV (tanb40) 5s discovery
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Conclusions

• A/H-gttt
• Run I results to be completed soon
• First glimpse of Run II data also on the way
• A/Hbb-gtbbbb
• Run I result excludes -gt 115 GeV at tanb60
• Run II with both experiments
• Set to exclude (discover) significant region of
  MSSM parameter space
• Optimistic about improvements from
• Triggers
• Jet resolution
• b-tagging