Properties of the hadronic system resulting fromν¯μpinteractions

The properties of the final-state hadronic system in antineutrino-proton charged-current interactions are presented. The events were observed in the Fermilab 15-foot hydrogen bubble chamber. The average energy of the events is ∼30 GeV, but there are some interactions beyond 100 GeV. The mean multiplicity of the charged hadrons varies as $〈n_C^H〉=(0.06\mathrm{}\pm 0.06)+(1.22\pm 0.03)\ln W^2$ for hadronic masses $W$ in the range $1.0<\mathrm{}{W}^2<50\mathrm{}$ ${\mathrm{GeV}}^2$. By contrast, the multiplicity depends only weakly on the four-momentum transfer between the leptons. The mean pion multiplicities for events with three or more charged tracks are found to be $〈n_{-}〉=1.64\mathrm{}\pm 0.04$, $〈n_0〉=1.16\mathrm{}\pm 0.13$, for ${\pi }^{-}$ and ${\pi }^0$ production, respectively. By comparing the number of positive tracks with ${\pi }^{-}$ data from neutrino production, we deduce a mean proton multiplicity $〈n_p〉$ of 0.53 ± 0.15. The single-particle distributions in both longitudinal and transverse momentum are found to be similar to those for nondiffractive production in hadronic collisions. The fragmentation properties of the final-state $d$ quarks are compared to the expectations of the quark-parton model. The fraction of observed neutral-strange-particle production for events with three or more charged tracks is 0.08 ± 0.015 and is consistent with coming completely from associated production.