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Higgs and SUSY at the LHC

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BR decreases as mA increases ~6 jet lepton missing energy. SM background uncertain? ... potential for discrimination seems promising! ATLAS. Searching for SUSY ... – PowerPoint PPT presentation

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Title: 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

3
(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)
4
Neutral Higgs production
Mass of H or h
5
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
6
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
7
Heavy neutral higgs (H,A)
8
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

9
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
10
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?
11
Charged higgs
  • When H is close to top mass
  • H -gt tbor
  • t -gt Hb
  • Revised analyses in progress

ATLAS
12
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?

13
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

14
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.

15
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
16
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
17
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
18
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
19
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
20
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

21
SUSY -gt h,H,A -gt bb
? susy signal ? susy bkg ? SM tt bkg
22
H0, A0 -gt SUSY -gt leptons
hep-ph/0303095
23
SUSY -gt light higgs
  • Region of parameter space where h is discoverable
  • cosmological bulk region

CMS note 2003-033 for summary
24
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
25
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

26
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.

27
Backup slides
28
SM-like higgs discovery
ATLAS
h ? tt requires multi-object t-jet, lepton trigger
29
Charged higgs
30
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-
31
mSUGRA Dilepton edge reach
32
SM-like higgs rate measurement
33
Overall SummaryTwo experiments, 30 fb-1,
charged and neutral higgs.
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