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Single Diffractive Higgs Production at the LHC *

Maria Beatriz Gay Ducati beatriz.gay@ufrgs.br. Single Diffractive Higgs Production at the LHC *. DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER. * Work with G. G. Silveira, M. M. Machado and M. V. T. Machado. Motivation Diffractive Physics Higgs production at LO

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Single Diffractive Higgs Production at the LHC *

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  1. Maria Beatriz Gay Ducati beatriz.gay@ufrgs.br SingleDiffractive Higgs Production at the LHC* DIFFRACTION 2010 – OTRANTO, ITALY, 10 – 15 SEPTEMBER * Work with G. G. Silveira, M. M. Machado and M. V. T. Machado

  2. Motivation Diffractive Physics Higgs production at LO Higgs production at NLO Inclusive and diffractive cross section Pomeron Structure Function Multiple Pomeron Scattering Results Conclusions Outlook

  3. Motivation • Compute single diffractive and Double Pomeron Exchange (DPE) production of the Standard Model Higgs Boson • Considering diffractive factorization formalism • Parametrization for the Pomeron Structure Function H1 Collaboration (2006) • Cross section computed at NLO accuracy • Gluon fusion process leading mechanism to the Higgs boson production • Gap survival probability rescattering corrections due to spectator particles • Single diffractive ratio computed for proton-proton collisions at the LHC • Estimations for the single and DPE events in the LHC kinematical regime

  4. The TEVNPH Working Group, 1007.4587 [hep-ph] Motivation • LHC opens a new kinematical region: • CM Energy in pp Collisions: 14 TeV 7x Tevatron Energy • Luminosity: 10 – 100 fb-1 10 x Tevatron luminosity • Evidences show new allowed mass range excluded for Higgs Boson production • Tevatron exclusion ranges are a combination of the data from CDF and D0

  5. Diffractive processes rapidity gap Exchange of a Pomeron with vacuum quantum numbers Pomeron with substructure DPDFs Diffractive distributions of quarks and gluons in the Pomeron Introduction MBGD, M. M. Machado and M. V. T. Machado, PRD What is the Pomeron ? • Diffractive structure function • Gap Survival Probability (GSP) • Cross sections at NLO

  6. Single diffraction in hadronic collisions One of the colliding hadrons emits Pomeron Partons in the the Pomeron interact with partons from the another hadron Absence of hadronic energy in the final state Heyssler et al, 9702.286 [hep-ph] Single diffractive Higgs production Regge factorization Rapidity gaps

  7. DPE Higgs production Double Pomeron Exchange in hadronic collisions Both colliding hadrons emit Pomeron Partons in the the Pomerons interact with each other Absence of hadronic energy in the final state P. D. Collins, An Introduction to Regge Theory and High Energy Physics Regge factorization Two rapidity gaps

  8. D. Graudenz et al. PRL 70 (1993) 1372 Higgs production • Focus on the gluon fusion • Main production mechanism of Higgs boson in high-energy pp collisions • Gluon coupling to the Higgs boson in SM triangular loops of top quarks Lowest order to gg contribution

  9. At NLO, these processes could occur Diagrams Quark consideredtop (high mass) Possible background expected for high pT Higgs production in gq and qq collisions Vertex corrections Real gluon radiation

  10. Partonic cross section M. Spira et al. 9504378 [hep-ph] • Lowest order parton cross section expressed by the gluonic width of the Higgs boson Quark Top gg invariant energy squared • dependence

  11. LO hadroproduction • Lowest order two-gluon decay width of the Higgs boson PDFs MSTW2008 • Gluon luminosity • Lowest order proton-proton cross section • Renormalization scale • s invariant pp collider energy squared

  12. M. Spira et al. 9504378 [hep-ph] QCD Corrections Three contributions • Involve virtual corrections for the subprocess and the radiation of gluons in the final state • Higgs boson production gluon-quark collisions and quark annihilation • Subprocesses contribute to the Higgs production at the same order of αs • Virtual corrections modify the lowest-order fusion cross section by a coefficient linear in αs

  13. NLO Cross Section • Gluon radiation two parton final states • Invariant energy in the channels • New scaling variable supplementing and • The final result for the pp cross section at NLO • Renormalization scale in αs and the factorization scale of the parton densities to be fixed properly

  14. NLO Cross Section • Coefficient contributions from the virtual two-loop corrections • Regularized by the infrared singular part of the cross section for real gluon emission • Infrared part • Finite τQ dependent piece • Logarithmic term depending on the renormalization scaleμ

  15. Delta functions • Contributions from gluon radiation in gg, gq and qq scattering • Dependence of the parton densities renormalization scale μ factorization scale M • Renormalization scale QCD coupling in the radiative corrections and LO cross sections

  16. dfunctions F+ usual + distribution Considering only the heavy-quark limitRegion allowed by Tevatron combination

  17. Diffractive cross section Single diffractive Double Pomeron Exchange Gluon distributions in the Pomeron Normalization Gluon distributions in the proton MSTW (2008) H1 parametrization (2006) Pomeron flux Gluon distributions (i ) in the Pomeron IP

  18. A. Aktas et al, Eur. J. Phys. J. C48 (2006) 715 H1 parametrization • Range of data 0.0043 < z < 0.8 • In this work, FIT B. • z is the momentum fraction of the Pomeron

  19. Gap Survival Probability (GSP) • Absorptive corrections by Multiple Pomeron Scattering • <|S|2> gap survival probability (GSP) Gap • A(s,b) diffractive process amplitude • PS(s,b) probability that no inelastic interactions occurs between remains particles Comparison between GLM and KKMRmodels 19

  20. Single diffraction M. Spira et al. 9504378 [hep-ph] Heyssler et al, arXiv:hep-ph/9702286 • ρ variable gives the renormalization/factorization scale dependence • Predictions to inclusive and diffractive cross sections at LO in agreement with other theoretical predictions NLO cross sections ~ 1.7 greater than LO cross sections

  21. Double Pomeron Exchange • DPE cross sections as Higgs mass function • Significant reduction of the diffractive cross section when applied the GSP • Difference about a factor 2 between GLM and KKMR models • Cross section and PDFs evaluated at NLO KKMR = 2.6 % GLM = 6 %

  22. Higgs production as ρ function (LO) Single Diffraction KKMR = 6 % GLM = 8 % Heyssler et al, arXiv:hep-ph/9702286 DPE KKMR = 2.6 % GLM = 6 % ρ = μ / MH Boonekamp et al, arXiv:hep-ph/0406061

  23. Higgs production as ρ function (NLO) Single Diffraction KKMR = 6 % GLM = 8 % DPE KKMR = 2.6 % GLM = 6 % ρ = μ / MH

  24. Conclusions Inclusive Single Diffractive Double Pomeron Exchange Higgs production atLHC energies at LO and NLO • Theoretical predictions • Estimate for cross sections as a function of Higgs Mass and ρ = μ/MH • Diffractive ratio computed using hard diffractive factorization and absorptive corrections • Values of diffractive LO cross section in good agreement with other theoretical predictions • Different predictions to NLO cross sections using two GSP models (KKMR and GLM) • Feasible value of cross sections for both GSP models SD ~ 50 - 70 fb DPE ~ 3 – 6 fb Very small diffractiveratios to Higgs Mass ~ 150 GeV at NLO without GSP SD ~ 2.5 % MBGD, G. G. Silveira PRD 78 113005 (2009) DPE ~ 0.5 %

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