Diffractive Higgs production at the LHC Alan Martin (Durham) 31 st John Hopkins Workshop Heidelberg, August 2007 H p p Prod. of Higgs in diff ve hadron-hadron collisions Otto Nachtmann et al. Phys,Lett. (1990)

Exclusive Higgs production at the LHC The price for rapidity gaps ?  Khoze, Martin, Ryskin O(1 GeV) ? far from IP

no emission when  ~ 1/k t ) > (d ~ 1/Q t ) i.e. only emission with k t > Q t calculated from multi-Pomeron multi-channel eikonal analysis of soft pp data S 2 = 0.02 at LHC S 2 = 0.05 at Tevatron

Description of ‘soft’ high energy pp interactions DL:  eff = t ---but nothing about inelastic int n Inclusion of multi-P effects essential: new analysis  bare ~ t ++ …. KMR ch eikonal full multi-Pomeron  total (LHC) ~ 95 mb S 2 Higgs (LHC) ~ 0.02 N* + + ….++= where

Prediction of  (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 =0.02 (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

 (pp  p+H+p) ~ 3 fb at LHC for 120 GeV Higgs if L = 60 fb -1, then 180 events efficiency of p taggers BR(H  bb) b,b tag efficiency polar angle cut mass window events

Background to pp  p + (H  bb) + p signal LO (=0 if m b =0, forward protons) gg  gg mimics gg  bb (P(g/b)=1.3%) after polar angle cut  0.3 Irreducibe bb  0.5 HO (gg) col.sing  bb+ng Soft emissions still suppressed by J z =0  ~ 0 Hard emissions if g not seen: extra gluon along beam M miss > M bb  ~ 0 extra g from initial g along b or b  0.2 Pomeron-Pomeron inelastic  0.06 B/S total B/S~1 assuming  M miss ~ 3  M ~ 5 GeV S~1/M 3, B~  M/M 6 : triggering, tagging,  M better with rising M for M=120 GeV 

hard P soft P d  /dy| y=0 units fb k T <5 GeV  M dijet /M bb =20%  M missing =4GeV signalbackgd

conventional signal for SM GeV Higgs

BBKM.  (first) corr n could be large and -ve, eikonal enhanced S 2 =0.02

BBKM find first corr n could be large and –ve. BUT…need to sum complete set of diagrams. terms alternate in sign ln Q T 2 Q T ~2GeV Analogous new “soft” analysis finds that even at low Q T, amp. is not completely suppressed Amp corr n affects only small Q T (large size dipoles) 1 st term sum 70%

The full set of enhanced diag. are included in  tot,  SD … in global soft fit The fit to “soft” data including enhanced rescatt. --redistributes abs. effects between eik. and enh. --find total S 2 same Analogously pred n for  tot (LHC) has v.weak model dep. since model fits existing soft data and there is log s energy behaviour  SD, sensitive to enh. effects, ~flat from 100 GeV, so expect no extra suppression of diffraction at LHC New global fit to “soft” data

Leading neutron prod. at HERA eikonal“enhanced” gap due to  exchange ~ exclusive Higgs     y i > 2 – 3 correction prop. to rap. interval prop. to  energy (negative) Prob. to observe leading neutron must decrease with  energy But expt.  flat  small enhanced correction KKMR ‘06 seennot seen

Level 1 trigger veto veto-trigger spoiled by pile-up 420-trigger spoiled by c buffer ? At present, plan to use 2 high E T jets/  (+ 420)

LHC every bunch crossing !

~0.01N for 420m ~0.03N for 220m

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

decoupling regime: m A ~ m H > 150 h ~ SM bbH ~ tan  VVH ~ 0 H,A   (bb) intense coup: m h ~ m A ~ m H ,WW.. coup. suppressed

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

Adapted from a preliminary plot of Tasevsky et al. (HKRSTW)

“standard candles” Possible checks of exclusive rates at the Tevatron “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 jet algorithm, hadronization etc pp  p +  + p low rate, but cleaner signal

pp  p +  + p KMR+Stirling

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

It means exclusive H must happen (if H exists) and probably ~ 10 fb within factor ~ 2.5. higher in MSSM 16 events observed QED: LPAIR Monte Carlo 3 events observed CDF Blessed this morning! CDF, Albrow et al.  (  = 10 fb for E T  >14 GeV at LHC one appears due to  0   ~0.09pb ~0.04pb

16 events were like this: 3 events were like this: Albrow one appears due to  0  

pp  p + jj + p Exptally more problematic due to hadronization, jet algorithms, detector resolution effects, QCD brem… Exclusive events have R jj = M jj /M X =1, but above effects smear out the expected peak at R jj = 1 (ExHuME MC)  excl ~R jj >0.8  excl (M>M jj )

Conclusion The pp  p+H+p cross section prediction is robust----factor 2 S/B~1 for SM h -----can be more for SUSY h, H. Checks are starting to come from Tevatron data ( ,dijet…) There is a 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. Need more expt al and theoretical work on L1 trigger The diffractive Higgs signals beautifully complement the conventional signals. Indeed there are SUSY Higgs regions where the diffractive signals are advantageous ---determine  M H, Yukawa H  bb coupling, searching for CP-violation in the Higgs sector