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Search for the Higgs Boson at the LHCSearch for the Higgs Boson at the LHC
W. AdamInstitut für Hochenergiephysik der ÖAW
Micro-summary of the Higgs discovery potential at LHC on the occasion of
FAKT-Tagung, Weyer, 26./27. Sep. 2004
Second “Physics at LHC” conferenceEmphasis on the physics programme &presentations by young physicistsAll 5 LHC experiments + theory
Organised by HEPHY (LOC: J.Hrubec,G.Mitselmakher, C.-E.Wulz)Held at the main building of the ÖAW~ 180 participants
The talk is based on material shown at PHLHC04 and other summer conferences
FAKT2004 Search for the Higgs Boson at the LHC 2
SM Higgs: experimental statusSM Higgs: experimental status
LEP EWWG, summer ‘04The situation after LEP:
Indirect (full EW fit)• Preferred value:
mH = 114 +69 -45 GeV(exp. errors only)
• Limit:mH < 260 GeV @ 95%CL
Precise values might still change,
but message is clear: a light Higgs
is favoured by the measurements.
Direct (LEP searches)• Observed (expected) limit
mH > 114.4 GeV (115.3GeV)• preferred value from -2lnQ ~115GeV
129GeV
114GeV
FAKT2004 Search for the Higgs Boson at the LHC 3
SM Higgs: experimental statusSM Higgs: experimental status
News from the Tevatron
Signatures: HWWbb(e)/()bb, HWZbb(ee//)bb (mH<130)
ggHWW* (e/)(e/) (mH>130)
(WH) x B(Hbb) for mH=115GeV < 12.4 pb (D0, e-channel)
< 5 pb (CDF)
FAKT2004 Search for the Higgs Boson at the LHC 4
SM Higgs: experimental statusSM Higgs: experimental status
xB(H-WW*) for mH=160GeV: < 5.7pb (D0), < 5.6pb (CDF)
Available summer ‘04: • ~400 pb-1/exp (recorded)• ~200 pb-1/exp (used)• 2009: 4.4 - 8.5 fb-1
FAKT2004 Search for the Higgs Boson at the LHC 5
The SM Higgs @ LHCThe SM Higgs @ LHC
Production:
mainly via gluon fusion
tt-fusion
W,Z fusion: increasinglyimportant at high masses
associated productionin the low mass region
FAKT2004 Search for the Higgs Boson at the LHC 6
SM Higgs: low massSM Higgs: low mass
Decay:
• bb dominates, but high multi-jet backgrounds and low mass resolution
• : BR low (10-3 to 10-4) - use small Higgs width and high resolution EM calorimetry
Material in front of calorimetry(e.g. CMS: full-Si tracker):
will need to complement withreconstruction of convertedphotons (under study)
FAKT2004 Search for the Higgs Boson at the LHC 7
SM Higgs: low massSM Higgs: low mass
H signal (CMS, mH=130GeV, 100fb-1)
ATL-PHYS-2003-024
Hbb much more challenging:use tt-fusion and top decay products
FAKT2004 Search for the Higgs Boson at the LHC 8
SM Higgs: production via VBFSM Higgs: production via VBF
Contributes ~10% at low masses, dominates at very high massesSpecial topology allows for easy tagging:• Forward jets• Central Higgs decay products
Low mass analysis decay channels:
• WW*, and
[email protected]@PHLHC04
Taus: need trigger (leptons and narrow jets) and offline enhancement (-lifetime tracking)
Contribution of VBFanalysis to total significance
FAKT2004 Search for the Higgs Boson at the LHC 9
SM Higgs: intermediate massSM Higgs: intermediate mass
Decay modes to WW and ZZ become important
FAKT2004 Search for the Higgs Boson at the LHC 10
SM Higgs: intermediate massSM Higgs: intermediate mass
HWW ll’X• strong background from top decays• need to use WW spin correlation• veto on central jets
P.Sphicas@PHLHC04
tt-background:1st jet pt vs.
For mH=170±10GeV: 10 fb-1 are sufficient for discovery
pT
FAKT2004 Search for the Higgs Boson at the LHC 11
SM Higgs: intermediate to high massSM Higgs: intermediate to high mass
The “easy” region: high probabilityfor decays to ZZ(*)
FAKT2004 Search for the Higgs Boson at the LHC 12
SM Higgs: intermediate to high massSM Higgs: intermediate to high mass
Golden channel HZZ 4
• high energy muons• Z mass constraint(s)• irreducible background: ZZ production
M.Sani@PHLHC04H 4, CMS preliminary
for high mass: decreasing sigma - need more BR: use llqq or ll
FAKT2004 Search for the Higgs Boson at the LHC 13
SM Higgs: summarySM Higgs: summary
Full range of Higgs boson masses can be covered - most of it already at low luminosity
CERN/LHCC 99-15 ATLAS TDR 15 CMS NOTE 2003/033
FAKT2004 Search for the Higgs Boson at the LHC 14
MSSM Higgs Boson MSSM Higgs Boson
5 Higgs bosons (h,H,A,H±)
• Usually parametrised using mA and tan (tree level). Stop-mixing at loop level!
• Important difference to searches at previous experiments: cascades via SUSY particles are possible! LEP HWG 2004-01
preliminaryB.Tuchming@PHLHC04
FAKT2004 Search for the Higgs Boson at the LHC 15
MSSM Higgs: H, AMSSM Higgs: H, A
“Decoupling regime”• High mA, high tan• decays to :
high BR, analyse leptonicand hadronic channels!
• decays to : lower BR, but ~1% mass resolution
“Intermediate regime”• mA<500GeV, tan<5-10• transition region between
couplings to u- and d-type• use AZH, H Wh,
H/A tt for very low tan
“Intense coupling regime”• Low mA, high tan• Higgses are almost degenerate
5 discovery reach
FAKT2004 Search for the Higgs Boson at the LHC 16
MSSM Higgses: hMSSM Higgses: h
“Decoupling regime”
• High mA, high tan
• h is SM-like (mh<150GeV!)
“Intermediate regime”
• mA<500GeV, tan<5-10
• h-couplings to VB and u-typesuppressed bb, decays
Large parts of the plane covered
VBF modes are important
FAKT2004 Search for the Higgs Boson at the LHC 17
MSSM Higgses: HMSSM Higgses: H±±
Production:• for low mass: tbH±
• for high mass: gb tH±
qq’ H±
gg H±H±
gg W±H±
Decay
• for mH>~130GeV: H± t(*)b dominates
• interesting for analyses: H±
FAKT2004 Search for the Higgs Boson at the LHC 18
MSSM Higgses: cascade decaysMSSM Higgses: cascade decays
In the MSSM Higgs bosons can decay to SUSY particles and/or be producedin SUSY decay cascades.
One scenario:
• M2 = 2*M1 = 350GeV, = 1TeV
• m(gluino) = 1200GeV• ms(squark) = 800GeV
“long” cascades via 03,4 and 0
1,2
mH<~200GeV accessible
N.Marinelli@PHLHC04
SUSY signal
SUSY bkg
SM bkg
FAKT2004 Search for the Higgs Boson at the LHC 19
More exotic scenariosMore exotic scenarios
Still more Higgs bosons …• CP-violation
Can add phases to MSSM parameters - major changes to all signatures• Invisible decays, e.g. to LSPs
excess would be visible, but interpretation?• Extra dimensions
e.g. Radion decays to Higgs bosons• Fermiophobic, gluophobic scenarios
Specific points in SUSY parameter space orin more general 2HDM models
Other scenarios• Technicolor
still alive .. LHC could look for decays of T to vector bosons.
• Strong VL-VL-couplingthe no-Higgs scenario: look for resonant WZ and non-resonant W+W+ scattering
FAKT2004 Search for the Higgs Boson at the LHC 20
Radion decaysRadion decays
Randall-Sundrum model: • warped extra dimensions; two branes (Planck & TeV plane)
Radion: scalar representation of the 5d gravitational field
Most promising channel: • hhbb : look for mass peaks
in the (narrow) and jj (broader) system• Other channels studied: bb, 4b
S.Gennai@PHLHC04
FAKT2004 Search for the Higgs Boson at the LHC 21
ConclusionsConclusions
In the Standard Model• LHC covers the full mass range• If discovered need to measure parameters
(mass, spin, CP, couplings, ..): major field of activity
In the MSSM:• The light Higgs is detectable in the full range• Some regions of parameter space are tricky• Analyses looking for SUSY decay chains are being developped• What’s about extensions? CP-violation?
Substantial progress also on the theoretical side, e.g.
• KNNLO for the SM Higgs production
• full one-loop + 2-loop RCs for large couplings in the MSSM
Still quite some work to be done before LHC startup!