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 pp  p + dijet +p, pp  p +  + p Alan Martin (IPPP,Durham)

also   H

SM

Branching fractions of SM Higgs

difficult region

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   even though BR(H   ) ~

conventional signal for SM GeV Higgs

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)

exclusive Higgs production at the LHC H p p 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 = M H …but we must calculate the price for rapidity gaps ?

pp  p + H + p If outgoing protons are tagged far from IP then  (M) = 1 GeV (mass also from H decay products) Very clean environment H  bb: QCD bb bkgd suppressed by J z =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   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 ++  FP letter of intent Khoze, Martin, Ryskin

Reliability of pred n the cross section is crucial Khoze, Martin, Ryskin

no emission when  ~ 1/k t ) > (d ~ 1/Q t ) i.e. only emission with k t > Q t

calculated using detailed 2-channel eikonal global analysis of soft pp data S 2 = at LHC S 2 = 0.05 at Tevatron M H =120GeV Lonnblad Monte Carlo S 2 = S 2 = 0.040

In summary,  (pp  p + H + p) contain Sudakov factor T g which exponentially suppresses infrared Q t region  pQCD S 2 is the prob. that the rapidity gaps survive population by secondary hadrons  soft physics  S 2 =0.026 (LHC) S 2 =0.05 (Tevatron)  (pp  p + H + p) ~ 3 fb at LHC for SM 120 GeV Higgs ~0.2 fb at Tevatron H

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

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

Background to pp  p + (H  bb) + p signal LO (=0 if m b =0, forward protons) gg  gg mimics gg  bb (P(g/b)=1%) after polar angle cut 0.2 |J z |=2 admixture (non-forward protons) 0.25 m b 2 /E T 2 contribution <0.2 HO (gg) col.sing  bb+ng Still suppressed for soft emissions. Hard emissions if g not seen: extra gluon along beam M miss > M bb  0 extra g from initial g along b or b bar 0.2 Pom-Pom inel. prod. B/S<0.5(  M bb /M PP ) 2 <0.004 B/S total B/S~1 assuming  M miss ~3 GeV DKMOR S~1/M 3, B~  M/M 6 : triggering, tagging,  M better with rising M for M=120 GeV 

 (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

BSM: motivation for weak scale SUSY Can stabilize hierarchy of mass scales:  M h 2 ~ g 2 (m b 2 -m f 2 ) Provides an explanation for Higgs mechanism (heavy top) Gauge coupling unification (at high scale, but < Planck) Provides a candidate for cold dark matter (LSP) Could explain the baryon asymmetry of the Universe There must be a light Higgs boson, M h < 140 GeV SUSY effects at present energies only arise from loops-- so the SM works well The Higgs sector is the natural domain of SUSY. Higgs vev induced as masses are run down from a more symmetric high scale

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

M h in GeV M h < 140

higgs pp  p 1 + higgs + p 2

decoupling regime: m A ~ m H large h = SM intense coup: m h ~ m A ~ m H ,WW.. coup. suppressed

e.g. m A = 130 GeV, tan  = 50 (difficult for conventional detection, but exclusive diffractive favourable) S B m h = GeV events m H = GeV m A = 130 GeV 1 5 SM: pp  p + (H  bb) + p S/B~10/10~1 with  M = 3 GeV, at LHC with 60 fb -1 enhancement

30 fb fb -1 5  signal at LHC exclusive signal

Diffractive: H  bb Yuk. coupling,  M H, 0 ++ Inclusive: H,A   wide bump m H =140 m H =160 L=60 fb -1 55 Tasevsky et al

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

CP violation in the Higgs sector h, H, A mix  H 1, H 2, H 3 H 1 could be light Carena mixing induced by stop loop effects…

Br.  in (fb) for H 1, H 2, H 3 production at the LHC S/B~M 5 cuts: (a) MeV, (c) 45<  (b)<135 0 fb

Tevatron can check exclusive Higgs prod. formalism

pp  p +  + p KMR+Stirling

Measurements with M  =10-20 GeV could confirm  H (excl) prediction at LHC to about 20% or less

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

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

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

Exclusive dijet and 3-jet prod 3-jet dijet E T >20GeV dijets dominate R j >0.8 3-jets dominate R j <0.7 RjRj KMR, in prep.

Conclusion The exclusive diffractive signal is alive and well. The cross section predictions are robust. Checks are starting to come from Tevatron data ( ,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  M 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  M H, Yukawa H  bb coupling, 0 ++ determin n ---searching for CP-violation in the Higgs sector

Expect a depletion of pp  p + bb + p events as R jj  1

Diffractive  production KMR+Stirling only order-of-magnitude estimates possible for  production

Conclusions Proton tagging is a valuable weapon in LHC Higgs physics pp  p + (H  bb) + p: S/B~1 if  M miss ~3 GeV, M miss = M bb especially for the important M H < 130 GeV region SUSY Higgs: unique signals in certain domains of MSSM tan  large (i) m h ~m H ~m A (  enhanced), (ii) m A large Azimuthal correlations are valuable spin-parity analyzer Distinguish 0 -- from 0 + Higgs “standard candles” at Tevatron to test excl. prod. mechanism pp  p +  + 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 +  + p low rate, but cleaner signal Exclusive double diff. prod. strongly favours 0 + Possibility of detecting CP-violating Higgs

Allow p’s to dissociate Larger signal---but no  QCD (bb) suppression, so use H 1   (…) E iT >7 GeV 1 + a sin 2  b cos 2  if CP cons. then a=0, |b|=1  p 1T p 2T fb