Higgs and SUSY at the LHC

1
Higgs and SUSY at the LHC

• Alan Barron behalf of the ATLAS and CMS
  collaborations

ICHEP-17 Aug 2004, Beijing
2
Outline

• Discovery and measurement of
• Higgs sector of MSSM
• SUSY partners of SM particles

• SUSY and Higgs discovery reviewed
• Reach, channels
• Focus on some recent work
• Determination of higgs v.e.v. ratio (tan b)
• SUSY spin measurement
• Mixed Higgs SUSY cascade decays

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(S)particle reminder
SM MSSM Higgs
SUSY
quarks (LR)leptons (LR) neutrinos (L?)
squarks (LR)sleptons (LR)sneutrinos (L?)
Spin-1/2
Spin-0
AfterMixing
?Z0 W gluon
BinoWino0Wino gluino
BW0
Spin-1
4 x neutralino
Spin-1/2
gluino

h0 H0 A0 H
H0H
2 x chargino

Spin-0
Extended higgs sector (2 doublets)
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Neutral Higgs production
Mass of H or h
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SM-like higgs discovery
h ? tt requiresexcellent low-pT lepton tau jet
trigger
fb-1
1 year _at_1034
1 year _at_1033
time
1 month _at_1033
ATLAS
Values for single experiment
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h Number of observable final states
Conservative in tan b
1 channel
2 channels
3 channels
4 channels
Excluded by LEP
5 channels
300 fb-1
several channels observable ?allows parameter
determination ?
Suppressed b, t
Suppressed g coupling
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Heavy neutral higgs (H,A)
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Measuring tan b (1)

• Ratio of v.e.v.s of the 2 MSSM Higgs doublets
• Important for understanding EWSB

• For large (gt5) tan b
• b Yukawa dominates s
• s ? tan2 b
• Measure s
• Compare to NLO

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Measuring tan b (2)

• Errors dominated by theoretical uncertainty on
  NLO cross-section
• With signal discovery at 5s, tan b measurable to
  35.

N.B. m, M2 kept fixed here
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Charged higgs production/decay

• Associated production with t and b quarks
• Decay H ?
• Very complicated final state!
• Combinatorial BG
• Also H ? t nt
• BR decreases as mA increases

6 jet lepton missing energy SM background
uncertain?
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Charged higgs

• When H is close to top mass
• H -gt tbor
• t -gt Hb
• Revised analyses in progress

ATLAS
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Overall Discovery Potential 300 fb-1

• Whole plane covered for at least one Higgs
• Large wedge area (intermediate tan b) where only
  h is observed
• No direct evidence for higgs beyond SM

ATLAS

• Can we distinguish between SM and extended Higgs
• sectors by parameter measurements?

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SM or Extended Higgs Sectors?
First look using rate measurements from VBF
channels (30fb-1)
ATLAS
BR(h?tt) BR(h?WW)
R
Deviation from SM expectation
DRMSSM-RSM/sexp
potential for discrimination seems promising!

• only statistical errors considered
• assumes Higgs mass exactly known

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Searching for SUSY

• If SUSY was exact wed have seen it already
• Variety of ways to induce SUSY masses
• Minimal super-gravity (mSUGRA)
• Anomaly mediated SUSY breaking (AMSB)
• Gauge mediated SUSY breaking (GMSB)
• Experimental emphasis is on building general
  toolkit of techniques based on types of
  signatures of above
• Generally search reach 2 TeV.

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SUSY Discovery - mSUGRA

• Finial discovery limit 2.5 TeV squark or
  gluino
• Initially will be limited by detector
  uncertainties, not SUSY stats!
• Also need to understand SM backgrounds

Gaugino mass term
Scalar mass term
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Slepton, squark, neutralino masses
M(c2)-M(c1) 105 GeV
Apply corrections for electron and muon energy
scale and efficiency Flavor Subtracted mass to
remove the contribution from uncorrelated SUSY
decays ee- mm- - em- - e-m
5 fb-1
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SUSY measurements - mass
q

• Mass measurements from exclusive cascade decays
• Mass differences well measured
• Typically limited by detector performance
• Of order 1
• Error in overall mass scale
• Unknown missing energy
• Of order 10

c01
p
p
c01
q
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SUSY SPIN _at_ LHC
Chiral coupling

• SUSY particles have spin differing by ½ from SM
• Discovering SUSY means measuring spins of new
  particles
• Possible at LHC?
• Investigation of mSUGRA Point 5

Measure Angle (or inv mass)
Spin-0
Spin-½
Polarise
Spin-½, mostly wino
Spin-0
Spin-½, mostly bino
Final state jet l l- ET ( decay of
other sparticle)
Similar technique allows measurement of tanb from
muon/electron asymmetry
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SUSY spin observable distributions
ATLAS
l-
parton-level
Events
Charge asymmetry,
spin-0
l
detector-level
ATLAS
Leptonjet invariant mass
-gt Measure spin-1/2 nature of neutralino-2 -gt
Also can measure scalar nature of slepton -gt
Success at several distinct points in parameter
space
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SUSY produces Higgs

q (720 GeV)

g (1200 GeV)
Strongly interacting, so high rate

g (600 GeV)


(1000 GeV)

Other points combinations also investigated



q (800 GeV)
(340 GeV)


(400 GeV)

h0, H0, A0, H

h0, H0, A0, H
(170 GeV)


(200 GeV)

(95 GeV)

• Provided Heavy higgs are lt150 GeV -gt produced
• Missing energy jet/lepton higgs decay-gtbb
• Apply very simple (general) analysis

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SUSY -gt h,H,A -gt bb
? susy signal ? susy bkg ? SM tt bkg
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H0, A0 -gt SUSY -gt leptons
hep-ph/0303095
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SUSY -gt light higgs

• Region of parameter space where h is discoverable
• cosmological bulk region

CMS note 2003-033 for summary
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H -gt SUSY

• Harder!
• Works in restricted area of m, M2 space
• Complements tau, tb analysis.

H? ? ?2,30 ?1,2? ? 3l ETmiss
hep-ph/0303093
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Conclusions (1)

• LHC SUSY and Higgs search strategies well
  developed
• Constantly being reviewed / developed
• New techniques in Higgs sector
• Production via Vector Boson Fusion
• Improves reach for MSSM benchmarks
• Couplings if only lightest higgs accessible
• Infer non-SM Higgs sector
• Measurement of tan b

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Conclusions (2)

• New SUSY techniques
• Lepton asymmetry
• Charge -gt spin determination
• Flavour -gt tan b
• Full likelihood event reconstruction
• 3rd generation squarks heavy gauginos
• (not covered in this talk)
• Combined SUSY Higgs
• Complimentary to standard Higgs searches
• Could help dis-entangle complex SUSY chains
• Much work going on for trigger, calibration,
  systematics.

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Backup slides
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SM-like higgs discovery
ATLAS
h ? tt requires multi-object t-jet, lepton trigger
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Charged higgs
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SUSY spin lepton asymmetry
Back to backin ?20 frame
quark
Probability
?
l
lepton
Phase space
Invariant mass
l-
m/mmax sin ½?

• Phase space -gt factor of sin ½?
• Spin projection factor in M2
• lq -gt sin2 ½?
• l-q -gt cos2 ½?

In presence of spin-correlations, lq invariant
mass is different for l and l-
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mSUGRA Dilepton edge reach
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SM-like higgs rate measurement
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Overall SummaryTwo experiments, 30 fb-1,
charged and neutral higgs.