Hadron diffractive processes: the structure of soft pomeron and colour screening

Abstract

On the basis of the experimental data on diffractive processes in πp, pp and pp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality of cross sections such as σ tot πp /σ tot pp → 1 at s → ∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion and proton (antiproton) in the impact parameter space of quarks, σ π ( r 1⊥ , r 2⊥ ; s) and σ p ( r 1⊥ , r 2⊥ , r 3⊥ ; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at | r i⊥ − r k⊥ | → 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented.

Quark combinatorics and meson-production ratios in hadronic Z 0 decays

“…7f). As was shown in [41], the sum of all these contributions (Figs. 7d, 7e etc.) results in the colour screening effect: the quark loop amplitude is nearly zero for the mentioned quark configurations at r qq < ∼ 0.2 fm (the existence of the colour screening effects in hadron production processes was emphasized long ago [43,44]).…”

“…The pomeron found under these constraints, Lipatov's pomeron [16], has an infinite set of poles in the j-plane; it is a suitable object for using it as a guide in the analysis of the soft interaction region. Such an extension of Lipatov's pomeron into the soft region has been already used in [41]; below we follow the results of [41].…”

“…7d: the quark-pomeron vertex is defined by the interaction of two reggeized gluons with a quark. The spin structure of such a vertex can be easily calculated (see [41], Appendix C) using the analysis of the leading-s terms in reggeon kinematics (large s and small t) for the vertex vector particle + fermion [42].…”

A possible two-component structure of the non-perturbative Pomeron

“…It is tempting to interpret the X-component as the gluonic component of the non-perturbative Pomeron and the Z-component as its flavour-dependent non-perturbative component. It is interesting to note that the possibility of a fully universal Pomeron was already considered in literature [10].Of course, there is no double counting. In the framework of the S-matrix Theory [11], there are 2 solutions of the Reggeon calculus : a critical Pomeron with intercept equal to 1, leading asymptotically to a (lns) η (η < 2) behaviour of the total cross-sections, and a supercritical Pomeron with intercept higher than 1, connected, at asymptotic energies, to the Froissart ln 2 s behaviour of the total cross-sections.…”

Universality of hadron cross section at ultrahigh energies

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