Discussion session : What can HERA still provide ?

9 April 2008

(based on works with A. Kaidalov, A. Martin and M. Ryskin )

V.A. Khoze (IPPP, Durham & PNPI, St. Petersburg )

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’.

Selected topics

y=-ln , =(1-x)

( essential also for calculations of the overlap (Pile-Up) backgrounds)

Higher sensitivity to the parameters of models for Soft Diffraction

FP: 420

RP: 220

H

(Graeme’s talk)

A way to reduce uncertainties in the predictions for CED processes associated with fg.

(to remove proton excitations)

Exposing the contribution of the Perturbative Pomeron to DDIS

(G. Watt, A.Martin and M. Ryskin (2006))

The perturbative .resolved Pomeron contribution.

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.

Nonperturbative resolved Pomeron.

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.

( ) / ( )R diffr incl

CONCLUSION

LET HERA DATA TALK !

Backup

3Pg

Revisiting diffractive dijet photoproduction

H1-ZEUS- NLO THEORY STILL UNRESOLVED

x

Factorization breaking caused by absorptive (rescattering) corrections.

ExpectationExpectation: Small size component-unsuppressed Large size component-suppressed. In the ‘ideal theoretical limit’ (KKMR-03) Experimental analysisExperimental analysis: ranges, within NLO QCD.

A word of cautionA word of caution: at large , the NLO may not be sufficient: large (Sudakov-like) effects.KKMR-03 proposal: to measure the ratio of the diffractive process to the inclusive production (similar to the CDF diffractive studies ) as a funct. of Q²

x2 (1/(1 )lns x

( ) / ( )R diffr incl

‘Direct’ ‘Resolved’

( agreem. withlead. neutrons)

(CDF-00)

Difficult to draw a definite conclusion.

(various theoretical and experimental uncertainties may cancel)

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 .

( 2.5 0.3 )YM GeV W

2YM

/ )/ (Y el J )/ (Y el

-a crucial ingredient for understanding diffraction (e.g. S² calc.)

Bare

A way to extract the information on (small rescatter. effects)

3Pg

3Pg

/ ( )p J Y

KMR-06

Importance of an explicit measurement of the Y-system mass spectrum.To perform a full triple-Regge analysis with different contributions quantified.

(by integration over ZEUS range)

YM

(small size comp. of the proton w.f.)

SD

growth due to Pomeroninteractions compensatedby stronger absorption,i.e. decrease of S2

Also a crucial ingredient of calculations of the overlap (PU)- backgrounds to CED production.

(+ RRP+PPR)

Leading Protons at the LHC

FP420 RP220

KMR-07