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HERA: Revisiting Proton Dissociation in Diffractive Production

This discussion session explores what HERA can still provide in terms of improved statistics and measurements for proton dissociation in diffractive J/ψ and Υ production, diffractive to exclusive dijets ratio, transverse momentum distribution, and the CED formalism.

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HERA: Revisiting Proton Dissociation in Diffractive Production

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  1. Discussion session : What can HERA still provide ? 9 April 2008 V.A. Khoze(IPPP, Durham & PNPI, St. Petersburg ) Selected topics (based on works with A. Kaidalov, A. Martin and M. Ryskin ) More detailed data on proton dissociation in diffractive J/ and  production (better statistics, M²-slicing). Improved statistics on exclusive - production (not sufficient at the moment). The ratio of diffractive to exclusive dijets. Transverse momentum distribution of secondaries in the ‘Pomeron fragmentation’.

  2. Higher sensitivity to the parameters of models for Soft Diffraction FP: 420 y=-ln , =(1-x) RP: 220 ( essential also for calculations of the overlap (Pile-Up) backgrounds)

  3. H

  4. (Graeme’s talk) (to remove proton excitations) A way to reduce uncertainties in the predictions for CED processes associated with fg.

  5. Exposing the contribution of the Perturbative Pomeron to DDIS (G. Watt, A.Martin and M. Ryskin (2006)) The perturbative .resolved Pomeron contribution. Nonperturbative resolved Pomeron. Measurements of the kt of secondaries in the ‘Pomeron fragmentation’ (edge of LRG). The kt distribution of the lowest jet should obey the power law – in marked contrast with the expectations based on Regge-factorization. Larger kt of the secondaries with the long power-like tail should be observed.

  6. Main Tests of the CED formalism with HERA data at a glance Better evaluation of the bare 3P vertex  Inelastic diffractive J/() (photo)production Generalized Gluon Distributions  Exclusive Y- (photo)production Probing the rescattering effects ( S²) Diffractive dijets ( ). Manifestation of Perturbative Pomeron  Transverse momentum distr. at the edge of LRG.

  7. CONCLUSION LET HERA DATA TALK !

  8. Backup

  9. Revisiting diffractive dijet photoproduction H1-ZEUS- NLO THEORY STILL UNRESOLVED Difficult to draw a definite conclusion. ‘Direct’ ‘Resolved’ (CDF-00) Factorization breakingcaused by absorptive (rescattering) corrections. Expectation: Small size component-unsuppressed Large size component-suppressed. In the ‘ideal theoretical limit’ (KKMR-03) Experimental analysis: ranges, within NLO QCD. A word of caution: at large , the NLO may not be sufficient: large (Sudakov-like) effects. KKMR-03proposal: to measure the ratio of the diffractive process to the inclusive production (similar to the CDF diffractive studies ) as a funct. of Q² ( agreem. with lead. neutrons) (various theoretical and experimental uncertainties may cancel)

  10. The Extraction of the Bare Triple-Pomeron Vertex Existing (ZEUS) data on J/ -still fragmentary Needed: - improved statistics; -distributions over ; - inelast. diffractive data; -more accurate measurements of ; -data on . • a crucial ingredient for understanding diffraction (e.g. S²calc.)  Bare (small size comp. of the proton w.f.)  A way to extract the information on (small rescatter. effects)  KMR-06 (by integration over ZEUS range)  Importance of an explicit measurement of the Y-system mass spectrum. To perform a full triple-Regge analysis with different contributions quantified.

  11. Leading Protons at the LHC SD KMR-07 growth due to Pomeron interactions compensated by stronger absorption, i.e. decrease of S2 FP420 RP220 (+ RRP+PPR) Also a crucial ingredient of calculations of the overlap (PU)- backgrounds to CED production.

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