Neutrino production of same-sign dimuons

In a sample of 670 000 charged-current neutrino events, 101 ${\mu }^{\mathrm{-}}$ ${\mu }^{\mathrm{-}}$ events have been observed, with 30 GeV<$E_{\nu }$9 GeV/c for both muons. After background subtraction, 18.5±13.9 events remain, yielding a prompt rate of (5.5±4.1)×${10}^{\mathrm{-}5}$ per charged-current event. A sample of 124 000 antineutrino events yields 15 ${\mu }^{+}$ ${\mu }^{+}$ events, giving 6.4±4.2 events after background subtraction and a prompt rate of (1.0±0.7)×${10}^{\mathrm{-}4}$ per charged-current event. The numbers and kinematic distributions of these events are consistent with standard model sources.