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Probing the Higgs sector at the LHC. SM Higgs detection at the LHC inclusive signals – brief review exclusive diffractive signals pp p + H + p calculation of H bb bar signal and background
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Probing the Higgs sector at the LHC • SM Higgs detection at the LHC inclusive signals – brief review exclusive diffractive signals pp p + H + p calculation of H bbbar signal and background “standard” candles at Tevatron: excl. c, gg, jj prod. • Higgs detection in MSSM Motivation for SUSY --- Higgs sector in SUSY exclusive diffractive signals --- advantages — 0--,0+ analysis CP violation in the Higgs sector University of Louvain, February 2005 Alan Martin (IPPP,Durham)
difficult region
A low mass Higgs (<130 GeV) is difficult to identify Hbb is dominant decay, but is swamped by the QCD background
Total width of SM Higgs G=1 GeV MH=120 GeV
pp p + H + p H bb
no emission when (l ~ 1/kt) > (d ~ 1/Qt) i.e. only emission withkt > Qt
calculated using detailed 2-channel eikonal global analysis of soft pp data S2 = 0.026 at LHC S2 = 0.05 at Tevatron Lonnblad Monte Carlo S2 = 0.026 S2 = 0.040 MH=120GeV
possible Tevatron “standard candles”
ppp + gg + p KMR+Stirling
KMR+Stirling Diffractive c production only order-of-magnitude estimates possible for c production
BSM: motivation for weak scale SUSY Can stabilize hierarchy of mass scales: dMh2 ~ g2(mb2-mf2) Gauge coupling unification (at high scale, but < Planck) Provides a candidate for cold dark matter (LSP) Could explain the baryon asymmetry of the Universe SUSY effects at present energies only arise from loops-- so the SM works well Provides an explanation for Higgs mechanism (heavy top) The Higgs sector is the natural domain of SUSY. Higgs vev induced as masses are run down from a more symmetric high scale There must be a light Higgs boson, Mh < 140 GeV
Mh < 140 Weiglein
H and h widths, compared to SM Higgs H --> hh and tt thresholds
Exclusive diffractive MSSM Higgs production Spin-parity analysis use angle j between two outgoing protons in the transverse plane to distinguish 0-- from 0+
ppp1 + higgs + p2 higgs
more peripheral p1T,p2T correlations reflect spin-parity of central system: can distinguish 0-- from 0+ pp p1 + H + p2
decoupling regime: mA ~ mH large h = SM intense coup: mh ~ mA ~ mH gg,WW.. coup. suppressed
SM: pp p + (Hbb) + p S/B~11/4 with DM = 1 GeV, at LHC with 30 fb-1 e.g. mA = 130 GeV, tan b = 50 (difficult for conventional detection, but exclusive diffractive favourable) S B mh = 124.4 GeV 71 3 events mH = 135.5 GeV 124 2 mA = 130 GeV 1 2 enhancement
5s signal at LHC 30 fb-1 300 fb-1
Motivation for CP-Violation in SUSY Models • In low energy SUSY, there are extra CP-violating phases beyond the CKM ones, associated with complex SUSY breaking parameters. • One of the most important consequences of CP-violation is its possible impact on the explanation of the matter-antimatter asymmetry. • Electroweak baryogenesis may be realized even in the simplest SUSY extension of the SM, but demands new sources of CP-violation associated with the third generation sector and/or the gaugino-Higgsino sector. • At tree-level, no CP-violating effects in the Higgs sector---CP violation appears at loop-level
gives the mixing between would-be CP-odd and CP-even sates, predominantly governed by stop induced loop effects Higgs Potential Quantum Corrections Main effect of CP-Violation is the mixing of the three neutral Higgs bosons In the base Gluino phase relevant at two-loop level. Guagino effects may be enhanced for large tan beta
CPX scenario: no lower bound on MH1 from LEP! • H1 decouples from the Z and H2 and H3 may be out of kinematic reach. • or reduced couplings of Hi to Z and extended regions were H2 decays H1H1 and the H1’s decay into b’s mH2 < 130 GeV major role of CP-violating effects Example: mH1 = 45 GeV, mH2 = 110 GeV, Not excluded No Universal lower limit on mH1 but (mt dep.) Including with in the analyses
Br.s in (fb) for H1, H2, H3 production at the LHC fb S/B~M-5 cuts: (a) 60<q(b or t)<1200, (b) piT>300 MeV, (c) 45<q(b)<1350
Allow p’s to dissociate Larger signal---but no sQCD(bb) suppression, so use H1 tt (…) EiT>7 GeV fb p1T j p2T 1 + a sin 2j + b cos 2j if CP cons. then a=0, |b|=1