First measurement of the $ u_{mu}$ charged-current cross section without pions in the final state on a water target

This paper reports the first differential measurement of the charged-current interaction cross section of $ u_{mu}$ on water with no pions in the final state. This flux-averaged measurement has been made using the T2K experiments off-axis near detector, and is reported in doubly-differential bins of muon momentum and angle. The flux-averaged total cross section in a restricted region of phase space was found to be $ sigma= (0.95 pm 0.08 (mbox{stat}) pm 0.06 (mbox{det. syst.}) pm 0.04(mbox{model syst.}) pm{} 0.08(mbox{flux}) ) times 10^{-38} mbox{cm}^2$ per n.