Measurement of ν¯μCC interactions with the ND280 detector of the T2K experiment

This paper presents a measurement of the $$\bar \nu _\mu$$ CC interactions both in neutrino and anti-neutrino data taking modes, using the near detector (ND280) of the T2K experiment. In neutrino beam mode a ∼ 4% intrinsic $$\bar \nu _\mu$$ component in the total neutrino flux is expected. The charged current interactions of $$\bar \nu _\mu$$ are selected combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeter of ND280. The measured ratio between the observed $$\bar \nu _\mu$$ beam component and the prediction is 1.01 ± 0.13, providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. This measure helps in the reduction of the large systematic uncertainty on the ratio $$\sigma _\bar \nu /\sigma _\nu$$ which affects the ν<inf>μ</inf> disappearance analysis. A precise measurement of $$\bar \nu _\mu$$ in anti-neutrino beam mode is also presented. This measurement is particularly of interest for the anti-neutrino data taking, since it is used to provide the ND280 constraint on flux and cross section parameters to the oscillation analyses.