Analysis of fragmentation functions of narrow band ν and $\overline{v}$ interactions on an isoscalar target

Neutrino and antineutrino interactions with two muons in the final state have been studied by the CCFR collaboration in the Fermilab Tevatron neutrino beam. The rate of neutrino- and antineutrino-induced prompt same-sign dimuon production in steel was measured using a sample of 220 μ⁻μ⁻ events and 15 μ⁺μ⁺ events with P_μ > 9 GeV/c, and energies between 30 GeV and 600 GeV. After background subtraction, the prompt rate of same-sign dimuon production is (0.53 ± 0.24) × 10⁻⁴ per ν_μ charged-current event and $\text{(0.52 ± 0.33) × 10}{}^{\mathrm{-4}}\text{per}\text{ν}{}_{\mathrm{\mu }}$ charged-current event. After demanding P_μ1 ≥ 9 GeV/c, P_μ2 ≥ 5 GeV/c and 30 ≤ E_ν ≤ 600 GeV a sample of 5044 $\text{ν}{}_{\mathrm{\mu }}\text{1062}\text{ν}{}_{\mathrm{\mu }}\text{induced}\text{μ}{}^{\mathrm{\mp }}\text{μ}{}^{\mathrm{\pm }}$ events are observed. The data support the slow rescaling model of charm production with a value of m_c = 1.31 ± .24 GeV/c². The CKM matrix element V_cd=.209±0.012 and the nucleon strangeness content, η_ε=.064_−0.00065^+0.00075 are measured with the strange sea x distribution found to be softer than its non-strange counterpart. The first measurements of the Q² dependence of the strange quark densities, ϰs(ϰ), are also presented.

The measurements of the z and p_T² distribution of hadrons produced in the interactions of 200 GeV muons with copper and carbon nuclei are shown in different x_Bj and virtual photon energy intervals. Effects of the jet scattering are seen at the lowest virtual photon energies while for energies above 70 GeV there is no evidence of these effects. Comparison with a theoretical model indicates that at high jet energies the parton fragmentation distance is greater than the nuclear radius and that the parton absorption cross section is less than 10 mb.

Quark fragmentation functions are studied in charged current ν and $\text{ν}$ interactions in deuterium. The W², Q² and y dependences are compared with the predictions of first order QCD and with those of higher twists. The W² dependence is a small effect in our kinematical range and our data are well linked to the higher W² muon scattering experiment. The Q² dependence of non singlet fragmentation functions is well reproduced by first order QCD but part of this dependence could be due to some low W kinematical effect. The y-z factorization breaking seems to be a low W effect but a small higher twist term, as predicted by Berger cannot be excluded.

The comparison of hadron production in deep inelastic lepton scattering on different nuclei allows information to obtained about the reinteraction of the final state hadrons, because the projectile particle has pointlike structure and does not undergo multiple reaction with the target.

A reduction in the multiplicity of fast forward produced hadrons was observed, which depends on the size of the target nucleus. This nuclear mainly depends on two kinematical variables, the virtual photon energy (ν) and the fraction of ν carried by the hadron observed (z_h). The explanation of the characteristic ν-dependence is still an unsolved problem.

The results of experiments performed in this field in the past 15 years are reviewed and discussed in the framework of intranuclear reinteraction models. A possible influence of the EMC effect on the hadron production in lepton nucleus scattering will also be considered.

More detailed experimental information in the range of ν of 10–30 GeV would be very desirable in order to discriminate between competing predictions for the hadron formation time and thus to develop a more consistent picture of the fragmentation process.