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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. K hoze ( IPPP, Durham & PNPI ). Main aims • MHV rules and SUSY at the service of ‘diffractive Higgs’

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MHV rule, (Super)Symmetries and ‘Diffractive Higgs’

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  1.  QCD and High Energy InteractionsLa 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)

  2. The LHC is a discovery machine ! • CMS & ATLASwere 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 • (luminositygoal ofδL ≤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 matchingΔ Mx ~δM (Missing Mass) RG p p (X. Rouby)

  3. 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. (Khoze-Martin-Ryskin1997-2008) -4 (CDPE) ~ 10  (incl) (A.Dechambre) 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

  5. 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->WWmode 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!

  6. some regions of the MSSM parameter space are especiallyproton taggingfriendly (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 channelbgds 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 & unusuallylarge 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

  7. for Higgs searches in the forward proton modeQCDbackgrounds 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

  8. (D. Kosower)

  9. NNLO (CFCA)

  10. 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

  11. (+ n soft gluons)

  12. (angular brackets)

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

  14. LO irreducible signal SM (120 GeV) Higgs backgd hard P 150 20 70 5 X1/8 soft P 9 0.14 ds/dy|y=0 units 10-3 fb kT<5 GeV DMdijet/Mbb=20% DMmissing=4GeV

  15. Conclusion 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. Insome BSMscenariospp p +(Hbb)+pmay become a Higgs discovery channelat 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. 

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

  17. 11. Thou shalt notdelay, theLHC start-upisapproaching.

  18. BACKUP

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

  20. beam direction case if a gluon jet is to go unobserved outside the CD or FD ( ) • violation of the equality : (limited bythe ) 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)

  21. Approximate formula for the background main uncertn. at low masses M- mass window over which we collect the signal b-jet angular cut : ( ) bothSand Bshould 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

  22. mb=0

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