MSSM Higgs in ATLAS

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MSSM Higgs in ATLAS
Bill Murray, November 2001
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Talk Overview

• Introduction to MSSM Higgs
• What restrictions do we know?
• ATLAS benchmarks
• Beyond the benchmark
• Conclusions

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Basics of SUSY Higgs

• 5 Higgses h, A, H, H and H-
• Mass relations
• So MA and b (or tan b) fix 5 masses (at tree
  level.)

Tree level
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Masses of SUSY Higgses
MH
LEP limit
Log tanb
MH

• Mh

Maximal mixing
MA
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Couplings of SUSY Higgs
Tree level
a is the h,H mixing h decouples for large MA
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Couplings of the h to t and Z
h-Z coupling
h-top coupling
SM like for MAgt150
Drops for MAlt150
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Coupling of the h to the b/t/m
Enhanced for low MA and high tan b. i.e. when the
top and Z couplings decrease Gives h radiation
off b quarks. Can be used at Tevatron as well as
LHC...
h-bottom coupling
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Coupling of H to the b/t/m and t
Enhanced at high tanb for mHgt125GeV
H-bottom coupling
H-top coupling
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Coupling of the A to the b/t/m
Enhanced for any large tanb Careful - the A
width also increases.
A-bottom coupling
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Existing Limits

• LEP benchmark scenarios
• No mixing
• Maximal mixing ?Least restrictive
• large m
• Maximal Mixing has
• MSUSY1TeV, M2200GeV, m-200GeV, mgluino800GeV,
  Xt2MSUSY

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Maximal Mixing Limit
Allowing MSSM scans (e.g. h??0?0 decays) makes
less than 1GeV difference in limit
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Limits on mA, tanb - large m
Two parameters tanb, MA m held to 1TeV Regions
of reduced Higgs to b coupling Probably LEP will
exclude this scenario eventually
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MSSM regions surviving LEP

• A heavy Decoupling region.
• The h looks like the SM Higgs, mass below 130GeV
• The A/H/H become quasi -degenerate in Mass
• Mass scale NOT KNOWN
• A light, tanb large.
• The h may be hard to find
• but couples to down type
  (b,t,m)
• The A/H/H become light and relatively easy to
  see

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What if there was a Higgs at 115?

• Essentially the whole unexcluded MSSM plane
  allows for a CP even Higgs at 115, depending upon
  loops.
• No guidance here!

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Tevatron Potential

• Can find h if we are in decoupling (heavy A)
  region, luminosity arrives, and mhlt120
• For High tan b, see

Significant chance of 1 Higgs
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Signatures in ATLAS

• All SM channels relevant (h?gg, tth?ttbb, H?ZZ)
• If A heavy, h behaves like SM Higgs (de-coupling)
• H may appear in SM channels
• Decays assuming super-partners too heavy
• A???, mm, tt, H ?hh, H?tb, cs, tn, t ? Hb?csb
• May also have
• c20 ?hc10 ,h ?c10c10, A/H/H ?sparticles
• Zoo of possible signatures, model dependent (h OK)

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Higgs from Weak Boson Fusion

• Motivation
• Additional potential for Higgs boson discovery
• Important for the measurement of Higgs boson
  parameters
• (couplings to bosons, fermions (taus), total
  width)
• Detection of an invisible Higgs
• proposed by D.Zeppenfeld et al. (several
  papers...)
• s 4 pb (20 of total cross section for mH 120
  GeV)
• however distinctive signature of
• - two high PT forward jets
• - little jet activity in
  the central region

Relevant to MSSM
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qqH ?qq WW ? qq l n l n

• - PYTHIA Signal and background simulations
• - El.weak backgrounds (t-channel vector boson
  exchange from matrix element calculation,
  D.Zeppenfeld et al.)
• - ISR FSR included (PYTHIA)
• Basic cuts on isolated leptons PT gt 20 GeV
• 
  ? lt 2.5
• Basic cuts on tagging jets PT gt 20 GeV
• 
  ?? gt 4.4
• Dominant background at that level tt production

PT(tot)
H
tt

• Additional rejection
• Mjj (inv. Mass of tag jets)
• PT (tot) PT(l1) PT(l2) Ptmiss PT(j1)
  PT(j2)
• (less sensitive to pile-up than jet-veto
  over large rap.)
• Jet Veto ( no jets with PT gt 20 GeV in ?
  lt 3.2 )

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Main background remaining tt background
(13.1 events) WW
el. weak background ( 7.1 events)
mH 130 GeV
mH 160 GeV
e m decays
e m decays

• Much to be done
• proper estimate of forward jet tag efficiencies
  in a full simulation,
• combination with ee and mm ignature,
  optimization of cuts

• For the same cuts significance is worse than in
  orig. publ. by Zeppenfeld et al. (ISR/FSR
  effects, jet calibration, efficiencies)
• However confirmed that WBF channel has a
  large discovery potential

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qqH ?qq t t ? qq l n n l n n
- Similar basic cuts as in WW analysis - Tau mass
reconstruction using collinear approximation -
Optimized cuts for em, ee and mm channels
mH 115 GeV 30 fb-1 all channels (em best
channel)
S 17.3 events B 11.4 events S/B gt 1

Preliminary, no systematics yet, l-had channel
to be added
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LHC discovery potential
Assuming SUSY particles are heavy Not all
channels shown
No holes at low L (30fb-1)

• Two or more Higgs can be observed over most
  of the parameter
• space ? disentangle SM / MSSM

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How many Higgses?
For low MA no little h visible If we see h. or H,
how do we know which it is?
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Discovery potential for 10 fb-1
Large part of plane can be explored in 2007
Hole
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Hole where h is hard to see
bbh?bbmm region expolits enhanced coupling Is
cross section calculated properly? (bb structure
functions?) Does experient allow for h width Can
we plug this gap??
mh
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A and H bosons

• Large tan b bbA and bbH enhanced
• sMSSM/sSM5000 tanb30, mA300GeV
• H/A seen through
• tt - 300 times rate, missing neutrinos
• mm - Good mass measurement

• Small tanb Would have been fun ?
  measurement of many couplings
• (including Hhh, AZh)

Recall mA gt 200 GeV A and H are
degenerate
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A/H ? ?? ? h? h??
Provides best reach for large mA.
Signature two stiff opposite-sign isolated
tracks (PT gt 40 GeV) PTmiss
or 1 b-tagged jet (bbA/H) Main challenge
reject QCD jet background. (already at
trigger-level) Feasible for mA gt 300 GeV (high
PT hadrons, larger PTmiss,
larger rejection from
isolation)
? RQCD 1010 ? QCD background ltlt 10
(tt Z/? ? ??)
mA 500 GeV tan b 25
mA 500 GeV tan b 25
b-tag requirement improves S/B
CMS PTmiss analysis 30 fb-1
Mass resolution 10
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Going beyond the Benchmark

• b?sg gives MHgt350GeV Benchmark simple!
• Susy particles light.
• Huge parameter space
• Reduce by assuming (normally) mSugra
• Discussed in next 2 transparencies.
• nMSSM
• Much more complex - I know no coherent study
• General 2 HDM
• Much more complex - I know no coherent study

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Higgs decays via SUSY particles
If SUSY exists search for H/A ? ?02?02
? ???01 ???01
5? contours
ATLAS SUGRA scan m0 50 - 250 GeV m1/2
100 - 300 GeV tan b 1.5 - 50 A 0 0
No CP violation
Exclusions depend on MSSM parameters (slepton
masses, m)
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How robust is this potential ?

• SUSY loops can enhance/suppress Higgs
  production
• (e.g. gg ? h) and decay (e.g. h ? gg)
• A/H/H? ? sparticles can compete with SM decays

Preliminary study mSUGRA impact of SUSY
on Higgs decays to SM particles is small
-- gg ? h ? ?? 10 smaller
-- tth/Wh ? ?? 30 smaller -- ttH ?
tt bb not affected -- BR (A/H/H? ?
SM particles) reduced by at most 40
Larger effects outside mSugra
However impact of mixing on couplings not
studied for all possible mixing scenarios ?
more work needed
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Searching for invisible Higgs ?
Signal qq ?qqVV ?qqH H?invisible

• Cut on
• Trigger (needs h of 4.9 for jets)
• Large jet-jet mass gt1200GeV/c2
• Large PT miss gt100GeV/c
• Isolation of PT miss
• Finally fjj

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Invisible Higgs ?
Assume no systematics in background...
? is fraction of SM Higgs rate
For MH (or MA), below 400GeV/c2 can see a SM
Higgs going 50 to invisible
But IMHO systematics serious
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Conclusions

• LHC has a large discovery potential for MSSM
  Higgs Bosons
• Some sign of MSSM Higgs sector should be
  observable
• Two or more Higgs bosons accessible in many
  cases.
• MA 200-500, tanbgt 15 gives all 5
• Vector Boson fusion channel significantly
  enhances the discovery potential
• Tau tau channel in the low mass region
• Enhanced WW channels
• Can it be used to see invisible Higgs decays ?
• New promising channels also in the MSSM section
• (Charged Higgs, had. Tau decays)
• To be done
• Need improved calculations (K-factors for S and
  B)
• MC work important (Follow Tevatron data ? MC ?
  LHC)
• new topics (CP violation, ...)
• Understand the measurements which can be made.