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Factorization Breaking in Diffractive Photoproduction of Dijets

Factorization Breaking in Diffractive Photoproduction of Dijets. Gustav Kramer University of Hamburg 15 april 20 04. 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 Gustav Kramer University of Hamburg 15 april 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. G. Kramer – Univ. Hamburg

  3. Kinematics Diffractive processes at HERA: Inclusive deep inelastic scattering: Diffractive deep inelastic scattering: Experimental cuts: H1 Coll., ICHEP 02 and EPS 03. G. Kramer – Univ. Hamburg

  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. G. Kramer – Univ. Hamburg

  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. G. Kramer – Univ. Hamburg

  6. Multi-Pomeron Exchanges Direct photoproduction: Resolved photoproduction:  Modification of the Regge trajectory  Factorization breaking G. Kramer – Univ. Hamburg

  7. DiffractivePhotoproductionofDijets Cross section: • Photon flux: Weizsäcker-Williams approximation G. Kramer – Univ. Hamburg

  8. FactorizableMulti-Pomeron Exchanges y-dependence: Photon flux xIP-dependence: Pomeron flux  Small correlations due to exp. cuts  Subleading Reggeon contribution G. Kramer – Univ. Hamburg

  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. G. Kramer – Univ. Hamburg

  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 G. Kramer – Univ. Hamburg

  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. G. Kramer – Univ. Hamburg

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

  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!) G. Kramer – Univ. Hamburg

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