Spin alignment and parity violation effects inρ 0 production in neutrino and antineutrino charged-current interactions

Abstract

Most of the measured events on hydrogen, deuterium and neon targets from BEBC at CERN and the 15-foot Bubble Chamber at Fermilab are combined to measure spin-density matrix elements for ρ0 production in the current-fragmentation region in neutrino and antineutrino charged-current interactions. The spin-alignment parameter η is found to be 0.08±0.11 for neutrino and 0.41±0.11 for antineutrino interactions. The parity-odd density matrix element Im(ρ10+ρ−10) is consistent with zero in both reactions. In the combined neutrino and antineutrino data an indication of parity violation is observed: Im ρ1−1=0.38±0.16 atxB>0.2,Q2>8 GeV2 andz>0.6.