Scaling and four-quark fragmentation

Abstract

The conditions for a scaling behaviour from the fragmentation process leading to slow protons are discussed. The scaling referred to implies that the fragmentation functions depend on the light-cone momentum fraction only. It is shown that differences in the fragmentation functions for valence-and sea-quark knock out give rise to scaling violations. It is proposed that these scaling violations are measured experimentally to put constraints on the four-quark fragmentation functions. Estimates suggest that with reasonable assumptions for the fragmentation functions large effects are to be expected.

The pion contribution to semi-inclusive deep inelastic scattering with slow baryons in the final state

“…In most models that are based on description of hadronization in terms of quark degrees of freedom [19][20][21] the cross-section is expected to be proportional to 1-Z near Z= 1. For the pionexchange such a simple asymptotic Z dependence is not entirely obvious, but the calculations show a linear dependence on 1 -Z for x > 0.05 (coming mainly from the linear dependence of the pion's structure function on 1 -x~), in agreement with experiment [22].…”

Slow proton production in semi-inclusive deep-inelastic neutrino scattering on hydrogen and deuterium

“…Note that z = 1 at x =0 corresponds to a hadron at rest. Because the neutrino can interact with both valence and sea quarks, it is convenient to distinguish between two types of processes, namely the fragmentation of a diquark when the neutrino interacts with a valence quark, and a four-quark fragmentation when it interacts with a sea quark [12]. The diquark fragmentation function has been parametrized by Bartl, Fraas, and Majerotto [11] who extended the original prescription of Field and Feynman to include the flavor degree of freedom and diquarks.…”

“…This will be discussed in (12) in which t =p, x"=x/(1z), g is the 7rNN coupling constant with g /4' =14.2, and f (t) =(Am ")/(A +t) is the vrNN form factor. Following Ref.…”