The cross section for semi-inclusive deep inelastic charged current neutrino scattering on hydrogen and deuterium in which a slow proton is observed in coincidence with the muon is computed as a function of Bjorken x and light-cone momentum of the detected proton. In the Impulse Approximation contributions from hadronization and (in case of the deuteron) the emission of a spectator nucleon are considered. In addition the probability for rescattering is computed. The results are compared to a recent analysis of the data from the WA25 (BEBC) experiment at CERN. 25.30.Pt,13.85.Hi

The cross section for the production of slow protons in deep-inelastic (anti)neutrino scattering on hydrogen and deuterium is described in terms of fragmentation of the spectator diquark and the emission of nuclear spectators. We find that the softening of the x distribution, when going from A =1 to A =2, is due to spectator emission.PACS number(s): 25.30.Pt, 13.85.Hi

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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.

A b s t r a c tThe semi-inclusive cross section for producing slow protons in charged current deep inelastic (anti-) neutrino scattering on protons and neutrons is calculated as a function of the Bjorken x and the proton momentum. The standard hadronization models based upon the colour neutralization mechanism appear to underestimate the rate of slow proton production on hydrogen. The presence of the virtual mesons (pions) in the nucleon leads to an additional mechanism for proton production, referred to as spectator process. It is found that at low proton momenta both mechanisms compete, whereas the spectator mechanism dominates at very small momenta, while the color neutralization mechanism dominates at momenta larger than 1-2 GeV/c. The results of the calculations are compared with the CERN bubble chamber (BEBC) data. The spectator model predicts a sharp increase of the semi-inclusive cross section at small x due to the sea quarks in virtual mesons.