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Diffractive Dijet Photoproduction

This publication by Michael Klasen explores the factors affecting diffractive dijet photoproduction and its factorization at the LPSC Grenoble. It discusses the role of direct and resolved photons, survival probability, gluon density, and factorization scale dependence. The study also investigates the transition from gp to DIS and the importance of large ET in the process.

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Diffractive Dijet Photoproduction

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  1. Diffractive Dijet Photoproduction Michael Klasen LPSC Grenoble April 28, 2005

  2. Publications • With G. Kramer • PLB 508 (2001) 259: g p  2 jets+n • EPJC 38 (2004) 39: g p  2 jets+p • PRL 93 (2004) 232002: g*p  2 jets+p + 1 paper in preparation Michael Klasen, LPSC Grenoble

  3. Hard diffraction:  Does factorization hold? Deep inelastic scattering: Yes  Direct photoproduction Hadroproduction: No  Resolved photoproduction Why next-to-leading order?  stot =sdir(xg,Mg)+sres(xg,Mg)  AtLOxg=1,butatNLOxg1  log(Mg)-dependence cancels Diffr. hadroproduction of dijets: CDF Coll., PRL 84 (2000) 5043 Motivation Michael Klasen, LPSC Grenoble

  4. Higgs Production at the LHC MH = 120 GeV – V. Khoze, A. Martin, A. Roeck, M. Ryskin, EPJC 25 (2002) 391 Michael Klasen, LPSC Grenoble

  5. Diffractive Higgs Production V. Khoze, A. Martin, M. Ryskin, EPJC 26 (2002) 229 Michael Klasen, LPSC Grenoble

  6. Diffractive processes at HERA: H1 Coll., EPS 2003 and DIS 2004 Inclusive DIS: Diffractive DIS: Experimental cuts: Kinematics Michael Klasen, LPSC Grenoble

  7. Double factorization: G. Ingelman, P. Schlein, PLB 152 (1985) 256 Hard QCD factorization: Regge factorization: Pomeron flux factor: Pomeron tracectory: Diffractive Parton Distributions Michael Klasen, LPSC Grenoble

  8. Diffractive deep inelastic scattering: J.C. Collins, PRD 57 (1998) 3051 Light cone coordinates: qm = (q+,q-,qT) Leading regions: H: qm  O(Q) J: lm  (0,Q/2,0T) A: |km|« O(Q) Soft gluon attachments: Poles in k+-plane: Finalstate: Upper half-plane Initial state: Lower half-plane Proof of Hard Factorization Michael Klasen, LPSC Grenoble

  9. Direct photoproduction:  Modify the Regge trajectory Resolved photoproduction:  Factorization breaking Multipomeron Exchanges X X Michael Klasen, LPSC Grenoble

  10. Diffractive Photoproduction of Dijets Cross section: Photon flux: Weizsäcker-Williams approximation Michael Klasen, LPSC Grenoble

  11. y-dependence: Photon flux  Small correlations due to exp. cuts xIP-dependence: Pomeron flux  Subleading Reggeon contribution Factorizable Multipomeron Exchanges Michael Klasen, LPSC Grenoble

  12. Hadronic collisions: Survival probability: Opacity / optical density: Ki = 1  g Kaidalov et al., EPJC 21 (2001) 521 Photoproduction: Generalized vector meson dominance: JPC= 1--: g  r, w, … Fittedparameters(W = 200 GeV): Total cross section:stot (rp)=34mb Pomeron slope: B = 11.3 GeV-2 Transition probability: g = 0.6  ZEUS Coll., EPJ C2 (1998) 247  H1 Coll., EPJ C13 (2000) 371 Survival probability: R  |S|2  0.34 Kaidalov et al., PLB 567 (2003) 61 Two-Channel Eikonal Model Michael Klasen, LPSC Grenoble

  13. xg-dependence: Direct/resolved photons  At LO, R = 1 agrees better with data! zIP-dependence: Gluon density in pom.  Smaller uncertainties in 1/s ds/dzIP No Sign of Factorization Breaking at LO Michael Klasen, LPSC Grenoble

  14. xg-dependence: Direct/resolved photons  Large K-Factor  Survival probability zIP-dependence: Gluon density in pom.  Reduced scale uncertainties at NLO Non-FactorizableMultipomeronExchanges Michael Klasen, LPSC Grenoble

  15. But: Data also support direct suppression! Michael Klasen, LPSC Grenoble

  16. Inclusive photoproduction: MK, Rev. Mod. Phys. 74 (2002) 1221 Diffractive photoproduction: MK, G. Kramer, EPJC 38 (2004) 39 Factorization Scale Dependence Michael Klasen, LPSC Grenoble

  17. Hadronization Corrections  Observable and model dependent! Michael Klasen, LPSC Grenoble

  18. Importance of large ET: Direct process dominates IS singularity less important Hadronization corrections small Experimentallydirectlyaccessible Less sensitive than xg Result: Suppressed result agrees Unsuppressed 50% too low How can we learn more? Critical role of IS singularity Transition from gp to DIS ET-Distribution Michael Klasen, LPSC Grenoble

  19. Q2-dependence: MK, G. Kramer, PRL 93 (2004) 232002 zIP-dependence: MK, G. Kramer, PRL 93 (2004) 232002 High- to Low-Q2 Transition in DIS Michael Klasen, LPSC Grenoble

  20. Factorization Scale Dependence MK, G. Kramer, to appear Michael Klasen, LPSC Grenoble

  21. Q2-dependence: MK, G. Kramer, to appear zIP-dependence: MK, G. Kramer, to appear Factorization Scheme Dependence Michael Klasen, LPSC Grenoble

  22. Components of Parton Densities in Photon • SaS parameterizations allow for separation: • Anomalous component: Resummation of IS singularity • Hadronic component: Vector meson dominance model • VMD component suppressed: • 10-4 for Q2 70 GeV2 • 10-2 for Q25 GeV2 • Anomalous component dominates: • Direct higher order contributions • Known from inclusive low-Q2 production Michael Klasen, LPSC Grenoble

  23. Conclusions Hard diffraction: Factorizable or not? • Deep inelastic scattering: Yes  Diffractive parton densities • Hadronic scattering: No  Multipomeron exchanges • Important application: Diffractive Higgs production at LHC Diffractive photoproduction of dijets: Initial state singularity at NLO • Direct / resolved photoproduction: xg and Mg dependence • (Non-) factorizable multipomeron exchanges Two-channel eikonal model: • Generalized vector meson dominance: g  r, w, … • Rapidity gap survival probability: R = 0.34 Related process: • Leading neutron with p-exchange (NB: fq/p, not fg/IP!) Michael Klasen, LPSC Grenoble

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