We report the first observation of off-axis neutrino interactions in the
MiniBooNE detector from the NuMI beamline at Fermilab. The MiniBooNE detector
is located 745 m from the NuMI production target, at 110 mrad angle
(6.3∘) with respect to the NuMI beam axis. Samples of charged current
quasi-elastic νμ and νe interactions are analyzed and found to be
in agreement with expectation. This provides a direct verification of the
expected pion and kaon contributions to the neutrino flux and validates the
modeling of the NuMI off-axis beam.Comment: 4 pages, 5 figures, Submitted to Phys. Rev. Let