Measurement of the $ν_μ$ flux and inclusive charged current cross section at T2K's near detector (1311.4800v1)

Abstract: We present the first measurement of the muon neutrino spectrum at the T2K near detector, ND280, using the data collected at the JPARC acc\ elerator facility in Tokai, Japan. ND280 is located 280 meters downstream from the target and 2.5$^\circ$ off-axis from the direction of the beam. The measured spectrum at ND280 constrains the flux and cross section uncertainties\ in the T2K oscillation analysis. We select inclusive charged-current (CC) events from muon \ neutrinos in ND280. These are separated into a charged current quasi-elastic (CCQE) enhanced sample and a CC non\ -QE sample. We then fit the muon spectrum for both samples to extract flux and cross section parameters, which are used as inputs into T2K's os\ cillation analysis. We separately produce a flux-averaged differential inclusive CC cross-se\ ction in the 2-dimensional plane of muon momentum and angle. For the cross-section measurement the flux is given by the MC and tuned to data from the NA61 experiment. We present the event selection, detector uncertainties, and final measurement result for both the spectrum and for the cross-section.