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Factorization Breaking in Diffractive Photoproduction of Dijets

Factorization Breaking in Diffractive Photoproduction of Dijets. Michael Klasen UJF / LPSC Grenoble 26 march 2004. Motivation Diffractive parton densities Multipomeron exchanges Direct and resolved photoproduction Conclusions. Motivation. Hard diffraction:

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Factorization Breaking in Diffractive Photoproduction of Dijets

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  1. Factorization Breaking in Diffractive Photoproduction of Dijets Michael Klasen UJF / LPSC Grenoble 26 march 2004 Motivation Diffractive parton densities Multipomeron exchanges Direct and resolved photoproduction Conclusions

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

  3. Kinematics Diffractive processes at HERA: Inclusive deep inelastic scattering: Diffractive deep inelastic scattering: Experimental cuts: H1 Coll., ICHEP 02 and EPS 03. Michael Klasen - LPSC Grenoble

  4. Diffractive Parton Distributions Double factorization: 1. Hard QCD factorization: 2. Regge factorization: Pomeron flux factor (integrated over t): Pomeron trajectory: Ingelman, Schlein, PLB 152 (1985) 256. Michael Klasen - LPSC Grenoble

  5. Proof of Hard QCD Factorization Diffractive deep inelastic scattering: 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 J.C. Collins, PRD 57 (1998) 3051. Michael Klasen - LPSC Grenoble

  6. Multi-Pomeron Exchanges Direct photoproduction: Resolved photoproduction:  Modification of the Regge trajectory  Factorization breaking Michael Klasen - LPSC Grenoble

  7. DiffractivePhotoproductionofDijets Cross section: • Photon flux: Weizsäcker-Williams approximation Michael Klasen - LPSC Grenoble

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

  9. Hadronic collisions: Photoproduction: Two-Channel Eikonal Model • Generalized vector meson dominance: • JPC= 1--:g  r, w, … • Fitted parameters (W = 200 GeV): • Total cross section: stot(rp)=34 mb • 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: Opacity / optical density: Ki = 1  g • Survival probability: • R  |S|2 0.34 Kaidalov et al., EPJ C21 (2001) 521. Kaidalov et al., PLB 567 (2003) 61. Michael Klasen - LPSC Grenoble

  10. Non-FactorizableMulti-Pomeron Exchanges xg-dependence: Direct/resolved photons zIP-dependence:  In LO, R = 1 agrees better with data!  Smaller uncertainties in 1/s ds/dz Michael Klasen - LPSC Grenoble

  11. R = fg/IP  fIP/p / fg/p with M12 = xg zIPxIPW: R = sdiffr. / sincl. with full kinematics: Diffractive / Inclusive Production CTEQ5M1 CTEQ6L A. Kaidalov et al., PLB 567 (2003) 61. MK, G. Kramer, hep-ph/0401202. Michael Klasen - LPSC Grenoble

  12. Inclusive photoproduction: Diffractive photoproduction: Factorization Scale Dependence CTEQ5M1 CTEQ6L MK, Rev. Mod. Phys. 74 (2002) 1221. MK, G. Kramer, hep-ph/0401202. Michael Klasen - LPSC Grenoble

  13. Conclusions Hard diffraction: Factorizable or not? • Deep inelastic scattering: Yes.  Diffractive parton densities • Hadronic scattering: No.  Multipomeron exchanges • Diffractive photoproduction of dijets 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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