Measurement of Muon-Neutrino and -Antineutrino Scattering off Electrons

Abstract

An aluminium spark chamber of 19 tons fiducial weight was exposed to the CERN neutrino beam. Possible cases of (ν̄)μ e scattering were selected by requiring an isolated shower at an angle < 5° to the indirection with an energy between 0.2 and 2 GeV, and satisfying the kinematics of elastic neutrino scattering off electron. In 508 (607) k-pictures of ν (ν̄)-film there were 25 (19) of such candidates found. Background gammas come mainly from neutral current induced π ⁰ production; less important is inverse β-decay. The background was determined experimentally in three consistent ways. After background substraction, a signal of 13.2 ± 5.3 ν _μe^- events and 16.1 ± 4.5 ν̄_μe^- events was left. After normalization for the fluxes used, the comparison of those rates diverges by 3 standard deviations from the V-A prediction. The total cross sections turn out to be 2.4 ±1.2 for ν μe^- and 5.4 ±1.7 for ν̄_μe^-, in units of 10^-42·Eν cm². They are in rather good agreement with the Salam-Weinberg theory.