Measurement of CC1PI$+$ on Water

A two-track event selection has been developed to get a 63{\%} pure CC1PI$+$ sample using ND280 Monte Carlo. We require exactly one forward going negatively charged good quality P0D-TPC matched track starting in the P0D fiducial region and exactly one P0D contained track with dE/dx PID applied. Two-parameter negative log likelihood fit in the $\mu^{\mathrm{-}}$ candidate momentum and $\theta $ angle phase space is performed to extract the fitted signal and background event rates for the water-in-P0D and water-out-P0D samples independently. Afterwards a water-in/water-out data subtraction technique is applied to obtain a CC1PI$+$ event rate on water exclusively.