Determination of the neutral current chiral coupling constants uL2, uR2, dL2 and dR2 from a neutrino and antineutrino deuterium experiment

The ratios of neutral-current to charged-current cross sections of v and v interactions, seperately, on proton and neutron targets have been measured. The Big European Bubble Chamber (BEBC), filled with deuterium and equipped with an external muon identifier (EMI) and an internal picket fence (IPF), was exposed to the CERN SPS (anti)neutrino wide-band beam. The measured ratios are Rvp= = 0.405 ± 0.024 ± 0.021, Rvn = 0.243 ± 0.013 ± 0.016, Rvp = 0.301 ± 0.027 ± 0.024 and Rvn = 0.490 ± 0.050 ± 0.037. (The first error is statistical and the second systematic). From combinations of these ratios the following neutral-current chiral coupling constants have been determined: uL2 = 0.099 ± 0.018 ± 0.008, dL2 = 0.202 ± 0.020 ± 0.019, uR2 = 0.020 ± 0.016 ± 0.009 and dR2 = 0.002 ± 0.017 ± 0.010. These results agree with the predictions of the SU(2) × U(1) standard electroweak model. Assuming ϱ = 1, the corresponding value of sin2 θ w is found to be 0.247 ± 0.029, whereas a two-parameter fit to the data yields sin2θw = 0.243 ± 0.046 and ϱ = 0.996 ± 0.041.