Direct calculation of the triple-pomeron coupling for diffractive DIS and real photoproduction (original) (raw)
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We present a unied direct evaluation of the triple-pomeron coupling A 3IP (Q 2 ) for diractive real photoproduction (Q 2 = 0) and deep inelastic scattering at large Q 2 in the framework of the dipole approach to the generalized BFKL pomeron. We demonstrate how the reaction mechanism changes from diraction excitation of the constituent quarks of the photon at Q 2 = 0 to excitation of the octet-octet colour dipole state of the virtual photon at large Q 2 . The small phenomenological value of A 3IP (0), which w a s a m ystery, is related to the small non perturbative correlation radius R c 0:3 fm for the perturbative gluons. We conrm the early expectations of weak Q 2 dependence of the dimensionful coupling A 3IP (Q 2 ) and predict that it rises by a factor 1:6 from real photoproduction to deep inelastic scattering. *
Virtual photon scattering at high energies as a probe of the short distance Pomeron
Physical Review D, 1997
Perturbative QCD predicts the behavior of scattering at high energies and fixed (sufficiently large) transferred momenta in terms of the BFKL pomeron (or short distance pomeron). We study the prospects for testing these predictions in two-photon processes at LEP200 and a possible future e ± e − collider. We argue that the total cross section for scattering two photons sufficiently far off shell provides a clean probe of BFKL dynamics. The photons act as color dipoles with small transverse size, so that the QCD interactions can be treated perturbatively. We analyze the properties of the QCD result and the possibility of testing them experimentally. We give an estimate of the rates expected and discuss the uncertainties of these results associated with the accuracy of the present theoretical calculations.
Journal of High Energy Physics, 2019
We analyze contributions to the heavy vector meson production with large transverse momentum in proton-proton and diffractive photon-proton scattering driven by an exchange of two Balitsky-Fadin-Kuraev-Lipatov Pomerons in the squared amplitudes. The Pomerons couple to a single parton and form a Pomeron loop closed by the vector meson impact factors. For the photon-proton case the diffractive cut of the Pomeron loop contributes, and for the inclusive hadroproduction one finds the loop with two cut Pomerons. We compute both of these Pomeron loop contributions and study in detail their properties. The results are then used to calculate the cross sections for diffractive J/ψ photoproduction with large transverse momentum at HERA and the correlated two Pomeron contribution for inclusive J/ψ and ϒ production cross sections at the LHC. Within a unified approach a good description of the photoproduction data is found, but correlated two Pomeron mechanism gives only a small contribution to h...
Diffractive DIS from the generalized BFKL pomeron. Predictions for HERA
Arxiv preprint hep-ph/ …, 1994
We present a microscopic QCD calculation of the cross section of diractive DIS and of the partonic structure of the pomeron from the dipole approach to the generalized BFKL pomeron. We carry out a detailed analysis of how one can factor out the non perturbative normalization of the diractive DIS cross section and its Q 2 evolution, which can be cast in the form of the conventional QCD evolution. We demonstrate that the pomeron cannot be treated as a particle with a uniquely dened structure function and ux in the proton. We nd a strong factorization breaking which can approximately be described by the two-component structure function of the pomeron, each component endowed with a dierent ux of pomerons in the proton. We predict a very weak Q 2 dependence of the diractive contribution to the proton structure function. *
Diffractive hard scattering with a coherent pomeron
Physics Letters B, 1993
Diffractive scattering involves exchange of a Pomeron to make a rapidity gap. It is normally assumed that to get a hard scattering in diffraction, one may treat the Pomeron as an ordinary particle, which has distributions of gluons and quarks. We show that this is not so: When we use perturbative QCD, there is a breakdown of the factorization theorem. The whole Pomeron can initiate the hard scattering, even though it is not point-like. Qualitatively, but not quantitatively, this gives the same effect as a delta function term in the gluon density in a Pomeron.
Probing the structure of the pomeron
The European Physical Journal C, 1999
We suggest that the pseudo-rapidity cut dependence of diffractive deep-inelastic scattering events at HERA may provide a sensitive test of models of diffraction. A comparison with the experimental cross section shows that the Donnachie-Landshoff model and a simple two-gluon exchange model of the pomeron model are disfavoured. However a model with a direct coupling of the pomeron to quarks is viable for a harder quark-pomeron form factor, as is a model based on the leading-twist operator contribution. We also consider a direct-coupling scalar pomeron model. We comment on the implications of these results for the determination of the partonic structure of the pomeron.
Pomeron Vertices in Perturbative QCD in Diffractive Scattering
2004
We analyse the momentum space triple Pomeron vertex in perturbative QCD. In addition to the standard form of this vertex which is used in the context of total crosssections at high energies and in the QCD reggeon field theory, there exists an alternative form which has to be used in the study of high-mass diffraction. We review and analyse the relation between these two versions. We discuss some implications for the BK-equation. In the second part of our paper we extend this analysis to the Pomeron-Odderon-Odderon vertex.