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V.A. K hoze ( IPPP, Durham )

V.A. K hoze ( IPPP, Durham ). Physics Backgrounds Revisited. A. Shuvaev & KMR arXiv:0806.1447  [hep-ph]. ( K hoze -M artin -R yskin 1997-2008). - 4. (CDPE) ~ 10  (incl). Not so long ago : between Scylla and .

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V.A. K hoze ( IPPP, Durham )

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  1. V.A. Khoze (IPPP, Durham) Physics Backgrounds Revisited A. Shuvaev & KMRarXiv:0806.1447 [hep-ph]

  2. (Khoze-Martin-Ryskin1997-2008) -4 (CDPE) ~ 10  (incl) Not so long ago: between Scylla and . Orders of magnitude differences in the theoretical predictions are now a history

  3. KMR-based arXiv:0712.0604 , PRD to appear soon A killing blow to the wide range of theoretical models. 2 (+10)  Excl. Events (CDF)

  4. 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. (B.Cox et al-06)  enhanced trigger strategy & improved timing detectors (FP420, TDR) MSSM situation in the MSSM is very different from the SM > 4 generations:enhancedHbbrate (~ 5 times ) Conventionally due to overwhelming QCD backgrounds, the direct measurement of Hbb is hopeless The backgrounds to the diffractive H bb mode are manageable!

  5. 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 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 in progress : (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 ……….. Not fully in MCs

  6. 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

  7. MHV-technique: an elegant way to write down the tree-level (and loop) helicity amplitudes in a compact way, automatically accounting for the possible cancellations between different terms, caused by gauge invariance and symmetry properties (e.g. Parke & Taylor-1986). Nowadays popular among (more) formal people E. Witten et al

  8. b b Real gluon radiation  Mercedes-like kinematics; ( KRS-2006) should be strongly reduced by the standard selection cuts. (can be accounted bySHERPA MC) g

  9. A.G. Shuvaev et al.arXiv:0806.1447 [hep-ph]

  10. Approximate formula for the background c C~0.5 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 + 1/4 ) at M≈120 GeV, M= 4GeV

  11. HKRSTW-07

  12. PRELIMINARY FenHiggs 2.6.2 M. Tesevsky, with new bgd

  13. HKRSTW-07

  14. PRELIMINARY FenHiggs 2.6.2 M. Tesevsky, with new bgd

  15. = -500 GeV PRELIMINARY

  16. Andy’s talk

  17. Shuvaev et al-08 arXiv:0806.1447 [hep-ph]

  18. 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 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)

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

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