Measurement of the reaction 12C( nu micro, micro-)X near threshold.

The reaction [sup 12]C([nu][sub [mu]],[mu][sup [minus]])[ital X] has been measured near threshold using a [pi][sup +] decay-in-flight [nu][sub [mu]] beam from the Los Alamos Meson Physics Facility and a massive liquid scintillator neutrino detector (LSND). In the energy region 123.7[lt][ital E][sub [nu]][lt]280 MeV, the measured spectral shape is consistent with that expected from the Fermi-gas model (FGM). However, the measured flux-averaged inclusive cross section [l brace][8.3[plus minus]0.7(stat)[plus minus]1.6(syst)][times]10[sup [minus]40] cm[sup 2][r brace] is more than a factor of 2 lower than that predicted by the Fermi-gas model and by a recent random phase approximation calculation.