A study of quasi-elastic muon (anti)neutrino scattering in he NOMAD experiment

We have studied the muon neutrino and antineutrino quasi-elastic (QEL) scattering reactions (vμn→μ-p and v-barμp→μ+n using a set of experimental data collected by the NOMAD collaboration. We have performed measurements of the cross-section of these processes on a nuclear target (mainly Carbon) normalizing it to the total vμ (v-barμ) charged current cross-section. The results for the flux averaged QEL cross-sections in the (anti)neutrino energy interval 3-100 GeV are <σqel>vμ = (0.92±0.02(stat)±0.06(syst))x10-38 cm2 and <σqel>v-barμ = (0.81±0.05(stat)±0.09(syst))x10-38 cm2 for neutrino and antineutrino, respectively. The axial mass parameter MA was extracted from the measured quasi-elastic neutrino cross-section. The corresponding result is MA = 1.05±0.02(stat)±0.06(syst) GeV. It is consistent with the axial mass values recalculated from the antineutrino cross-section and extracted from the pure Q2 shape analysis of the high purity sample of vμ quasi-elastic 2-track events, but has smaller systematic error and should be quoted as the main result of this work. Our measured MA is found to be in good agreement with the world average value obtained in previous deuterium filled bubble chamber experiments. The NOMAD measurement of MA is lower than those recently published by K2K and MiniBooNE collaborations. However, within the large errors quoted by these experiments on MA, these results are compatible with the more precise NOMAD value.