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Exclusive Higgs signals at the LHC

Exclusive Higgs signals at the LHC. SM Higgs detection at the LHC inclusive signals – a brief review exclusive diffractive signals pp  p + H + p calculation of H bb bar signal and background Exclusive SUSY Higgs signals Calibration processes at the Tevatron

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Exclusive Higgs signals at the LHC

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  1. Exclusive Higgs signals at the LHC • SM Higgs detection at the LHC inclusive signals – a brief review exclusive diffractive signals pp  p + H + p calculation of H bbbar signal and background • Exclusive SUSY Higgs signals • Calibration processes at the Tevatron pp  p + dijet +p, pp  p + gg + p Alan Martin (IPPP,Durham)

  2. also gg H

  3. SM

  4. Branching fractions of SM Higgs

  5. difficult region

  6. A low mass Higgs (<130 GeV) will challenging to identify Hbb is dominant decay, but is swamped by the QCD background Best chance is Hgg even though BR(Hgg) ~ 2. 10-3

  7. conventional signal for SM 110-130 GeV Higgs

  8. All plots are normalized to an integrated luminosity of 1 fb-1 and the signal is scaled by a factor 10 • Fraction of signal is very small (signal/background ~0.1)

  9. exclusive Higgs production at the LHC If the outgoing forward protons are measured far from the interaction point then it is possible to identify the Higgs and to make an accurate measurement of the missing mass = MH p H p …but we must calculate the price for rapidity gaps ?

  10. pp p + H + p Khoze, Martin, Ryskin If outgoing protons are tagged far from IP then s(M) = 1 GeV (mass also from H decay products) Very clean environment Hbb: QCD bb bkgd suppressed by Jz=0 selection rule S/B~1 for SM Higgs M < 140 GeV L(LHC)~60 fb-1~10 observable evts after cuts+effic Also HWW (L1 trigger OK) and Htt promising SUSY Higgs: parameter regions with larger signal S/B~10, even regions where conv. signal is challenging and diffractive signal enhanced----h, H both observable Azimuth angular distribution of tagged p’s spin-parity 0++  FP420 --- letter of intent

  11. Reliability of predn the cross section is crucial Khoze, Martin, Ryskin

  12. no emission when (l ~ 1/kt) > (d ~ 1/Qt) i.e. only emission withkt > Qt

  13. 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

  14. In summary, s(pp p + H + p) contain Sudakov factor Tg which exponentially suppresses infrared Qt region  pQCD H S2 is the prob. that the rapidity gaps survive population by secondary hadrons  soft physics  S2=0.026 (LHC) S2=0.05 (Tevatron) s(pp  p + H + p) ~ 3 fb at LHC for SM 120 GeV Higgs ~0.2 fb at Tevatron

  15. “enhanced” correction to sH(excl)? eikonal enhanced S2 =0.026 KMR: using 2-channel eikonal Gotsman,Levin,Maor.. Lonnblad, Sjodahl, Bartels,Bondarenko,Kutak,Motyka BBKMuse pert.thy.corrn could be large and negative,  s H(excl) reduced ? KMR  small effect

  16. Arguments why “enhanced” correction is small KMR ‘06 DY threshold Original Regge calc. required DY ~ 2-3 between Regge vertices (Recall NLL BFKL:  major part of all order resum has kinematic origin  DY ~ 2.3 threshold implied by NLL  tames BFKL) Applying to enhanced diagram need 2DY > 4.6, but at LHC only log(sqrt(s)/MH) available for yH=0 DY DY = 4.6 for MH=140 GeV Higgs prod. via enhanced diagram has v.tiny phase space at LHC

  17. Background to ppp + (Hbb) + p signal DKMOR assuming DMmiss~3 GeV LO (=0 if mb=0, forward protons) B/S gg  gg mimics gg  bb (P(g/b)=1%) after polar angle cut 0.2 |Jz|=2 admixture (non-forward protons) 0.25 mb2/ET2 contribution <0.2 HO (gg)col.sing bb+ng Still suppressed for soft emissions. Hard emissions if g not seen: extra gluon along beam Mmiss > Mbb 0 extra g from initial g along b or bbar 0.2 Pom-Pom inel. prod. B/S<0.5(DMbb/MPP)2 <0.004 for M=120 GeV  total B/S~1 S~1/M3, B~DM/M6 : triggering, tagging, DM better with rising M

  18. s(ppp+H+p) ~ 3 fb at the LHC For LHC integrated L = 60 fb-1 after allowing for: efficiency of the proton taggers BR(Hbb) b, b identification efficiency polar angle cut 180 events  10 observable exclusive evts with S/B~1

  19. 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

  20. SUSY Higgs: h, H, A, (H+, H--) There are parameter regions where the exclusive pp  p + (h,H) + p signals are greatly enhanced in comparison to the SM Selection rule favours 0++ diffractive production

  21. Mh < 140 Mh in GeV

  22. ppp1 + higgs + p2 higgs

  23. decoupling regime: mA ~ mH large h = SM intense coup: mh ~ mA ~ mH gg,WW.. coup. suppressed

  24. SM: pp  p + (Hbb) + p S/B~10/10~1 with DM = 3 GeV, at LHC with 60 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 10 events mH = 135.5 GeV 124 5 mA = 130 GeV 1 5 enhancement

  25. exclusive signal 5s signal at LHC 30 fb-1 300 fb-1

  26. Tasevsky et al Diffractive: H bb Yuk. coupling, DMH, 0++ 5s Inclusive: H,A tt wide bump L=60 fb-1 mH=140 mH=160

  27. 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

  28. CP violation in the Higgs sector h, H, A mix  H1, H2, H3 mixing induced by stop loop effects… H1 could be light Carena

  29. Br.s in (fb) for H1, H2, H3 production at the LHC fb S/B~M5 cuts: (a) 60<q(b or t)<1200, (b) piT>300 MeV, (c) 45<q(b)<1350

  30. Tevatron can check exclusive Higgs prod. formalism

  31. ppp + gg + p KMR+Stirling

  32. Measurements with Mgg=10-20 GeV could confirm sH(excl) prediction at LHC to about 20% or less

  33. CDF II Preliminary CDF Blessed this morning! Albrow 3 events observed 16 events observed It means exclusive H must happen (if H exists) and probably ~ 10 fb within factor ~ 2.5. higher in MSSM QED: LPAIR Monte Carlo

  34. 16 events were like this: Albrow 3 events were like this:

  35. Exptally more problematic due to hadronization, jet algorithms, detector resolution effects, QCD brem… ppp + jj + p Data plotted as fn. of Rjj = Mjj/MX, but above effects smear out the expected peak at Rjj = 1(ExHuME MC) Better variable: Rj = (2ET cosh h*)/MX highest ET jet h,ET with h*=h-YM Rj not changed by O(aS) final state radiation, need only consider extra jet from initial state. Prod.of other jets have negligible effect on Rj due to strong ordering We compute exclusive dijet and 3-jet prod (and smear with Gaussian with resolution s=0.6/sqrt(ET in GeV))

  36. ET>20GeV Exclusive dijet and 3-jet prod ET>20GeV dijet 3-jet dijets dominate Rj>0.8 3-jets dominate Rj<0.7 KMR, in prep. Rj

  37. Conclusion The exclusive diffractive signal is alive and well. The cross section predictions are robust. Checks are starting to come from Tevatron data (gg,dijet…) There is a very strong case for installing proton taggers at the LHC, far from the IP ---- it is crucial to get the missing mass DM of the Higgs as small as possible The diffractive Higgs signals beautifully complement the conventional signals. Indeed there are significant SUSY Higgs regions where the diffractive signals are advantageous ---determining DMH, Yukawa Hbb coupling, 0++ determinn ---searching for CP-violation in the Higgs sector

  38. Expect a depletion of pp  p + bb + p events as Rjj 1

  39. KMR+Stirling Diffractive c production 90 230 430 2000 9 20 50 130 only order-of-magnitude estimates possible for c production

  40. Conclusions Proton tagging is a valuable weapon in LHC Higgs physics pp  p + (H bb) + p: S/B~1 if DMmiss~3 GeV, Mmiss = Mbb especially for the important MH < 130 GeV region SUSY Higgs: unique signals in certain domains of MSSM tan b large (i) mh~mH~mA (s enhanced), (ii) mA large Exclusive double diff. prod. strongly favours 0+ Azimuthal correlations are valuable spin-parity analyzer Distinguish 0-- from 0+ Higgs Possibility of detecting CP-violating Higgs “standard candles” at Tevatron to test excl. prod. mechanism ppp + c + p high rate, but only an ord.-of-mag.estimate ppp + jj + p rate OK, but excl. evts have to be separated ppp + gg + p low rate, but cleaner signal

  41. 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

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