 MHV rule, (Super)Symmetries and ‘Diffractive Higgs’ QCD and High Energy Interactions La Thuile (Italy) , March 8-15 2008  MHV rule, (Super)Symmetries and ‘Diffractive Higgs’ V.A. Khoze (IPPP, Durham & PNPI) Main aims • MHV rules and SUSY at the service of ‘diffractive Higgs’ • major QCD backgrounds to Hbb production at the LHC in the forward proton mode (based on works with M.G. Ryskin, A.D. Martin and W.J. Stirling) Higgs sector study- one of the central targets of FP420 physics menu ADR (X. Rouby)

Lack of : p p RG X RG p p  High -pt signatures in the central region The LHC is a discovery machine ! CMS & ATLAS were designed and optimised to look beyond the SM  High -pt signatures in the central region But… Main physics ‘goes Forward’ Difficult background conditions, pattern recognition, Pile Up... The precision measurements are limited by systematics (luminosity goal of δL ≤5% , machine ~10%) Lack of : Threshold scanning , resolution of nearly degenerate states (e.g. MSSM Higgs sector) Quantum number analysing Handle on CP-violating effects in the Higgs sector Photon – photon reactions , … The LHC is a very challenging machine! The LHC is not a precision machine (yet) ! ILC/CLIC chartered territory p p RG Is there a way out? X YES  Forward Proton Tagging Rapidity Gaps  Hadron Free Zones matching Δ Mx ~ δM (Missing Mass) RG p p (X. Rouby)

Forward Proton Mode- Main Advantages for Higgs studies: For theoretical audience For experimental audience MHV rules, Super (symmetry) and ‘Diffractive Higgs’ at the LHC Irreducible Physics Backgrounds to Diffractive Higgs Production at the LHC (K.G) Forward Proton Mode- Main Advantages for Higgs studies: • Measurement of the Higgs mass via the missing mass technique (irrespectively of the decay channel) •Direct H bb mode opens up (Hbb Yukawa coupling); unique signature for the MSSM Higgs sector. •Quantum number/CP filter/analyzer •Cleanness of the events in the central detectors.

-4 (CDPE) ~ 10  (incl) (A.Dechambre) (Khoze-Martin-Ryskin 1997-2008) New CDF Excl. dijet results: A killing blow to the wide range of theoretical models. not so long ago: between Scylla and Charibdis: orders of magnitude differences in the theoretical predictions are now a history

situation in the MSSM is very different Studying the MSSM Higgs Sector without ‘clever hardware’: for H(SM)bb at 60fb-1 only a handful of events due to severe exp. cuts and low efficiencies, though S/B~1 . But H->WW mode at M>135 GeV. (ADR,B.Cox et al-06)  enhanced trigger strategy & improved timing detectors (FP420, TDR) MSSM situation in the MSSM is very different from the SM SM-like > Conventionally due to overwhelming QCD backgrounds, the direct measurement of Hbb is hopeless The backgrounds to the diffractive H bb mode are manageable!

For the channel bgds are well known and incorporated in the MCs: some regions of the MSSM parameter space are especially proton tagging friendly (at large tan  and M , S/B ) KKMR-04 HKRSTW, 0.7083052[hep-ph] B. Cox, F.Loebinger, A.Pilkington-07 Myths MC For the channel bgds are well known and incorporated in the MCs: Exclusive LO - production (mass-suppressed) + gg misident+ soft & hard PP collisions. Reality The background calculations are still not fully complete: (uncomfortably & unusually large high-order QCD and b-quark mass effects). About a dozen various sources (studied by Durham group)  admixture of |Jz|=2 production.  NLO radiative contributions (hard blob and screened gluons)  NNLO one-loop box diagram (mass- unsuppressed, cut-non-reconstructible)’  ‘Central inelastic’ backgrounds (soft and hard Pomerons)  b-quark mass effects in dijet events – still in progress potentially, the largest source of theoretical uncertainties! coming soon

for Higgs searches in the forward proton mode QCD backgrounds are suppressed by Jz=0 selection rule and by colour, spin and mass resolution (M/M) –factors. (KMR-2000) There must be a god Do not need many events to establish cleanly that the Higgs is a scalar and to measure the mass

(D. Kosower)

NNLO (CFCA)

Works is progress : W.J. Stirling et al, A. Shuvaev et al Preliminary results of calculations with the SL accuracy- very promising: a factor of 8 lower than the Born expectation (A. Shuvaev et al ) Good

(+ n soft gluons)

(angular brackets)

‘Conventional’ MC algorithms cannot be used kills soft gluon log no collinear logs ‘Conventional’ MC algorithms cannot be used

150 20 70 5 soft P 9 0.14 signal backgd hard P ds/dy|y=0 units 10-3 fb SM (120 GeV) Higgs signal LO irreducible backgd hard P 150 20 70 X 1/8 5 soft P 9 0.14 ds/dy|y=0 units 10-3 fb kT<5 GeV DMdijet/Mbb=20% DMmissing=4GeV

 Conclusion In some BSM scenarios pp p +(Hbb) +p may become a Higgs Strongly suppressed and controllable QCD backgrounds in the forward proton mode provide a potential for direct determination of the Hbb Yukawa coupling, for probing Higgs CP properties and for measuring its mass and width. In some BSM scenarios pp p +(Hbb) +p may become a Higgs discovery channel at the LHC. Further bgd reduction may be achieved by experimental improvements, better accounting for the kinematical constraints, correlations….. The complete background calculation is still in progress: (unusually & uncomfortably large high-order QCD effects, Pile-Up at high lumi). A clear downward tendency. 

 FP420, It is now or never Such opportunities come rarely UK Such opportunities come rarely –let’s not waste this one! FP420, It is now or never

11. Thou shalt not delay, the LHC start-up is approaching.

BACKUP

A killing blow to the wide range of theoretical models. Visualization of QCD Sudakov formfactor A killing blow to the wide range of theoretical models. d

 radiation from the screening gluon with pt~Qt :  beam direction case if a gluon jet is to go unobserved outside the CD or FD ( ) violation of the equality : (limited by the ) contribution is smaller than the admixture of Jz=2. KRS-06 b-direction case (HCA) 0.2 ( R/0.5)² (R –separation cone size) Note :  soft radiation factorizes  strongly suppressed is not a problem,  NLLO bgd  numerically small  radiation from the screening gluon with pt~Qt : KMR-02 HC (Jz=2) LO ampt. ~ numerically very small  hard radiation - power suppressed MHV results for gg(Jz=0)ggg(g) amplitudes (dijet calibration, b-mistag)

Approximate formula for the background main uncertn. at low masses M- mass window over which we collect the signal  b-jet angular cut : ( )  both S and B should be multiplied by the overall ‘efficiency’ factor  (combined effects of triggers, acceptances, exp. cuts, tagging efficienc., ….),  ~4.2 % (120 GeV)  g/b- misident. prob. P(g/b)=1.3% (ATLAS) Four major bgd sources ~ (1/4 +1/4 + (1.3)²/4 + 1/2 ) at M≈120 GeV, M= 4GeV

mb=0