Experimental study of neutrino absorption on carbon

The process of electron emission from \ensuremath{\sim}30 MeV neutrino absorption on carbon, $^{12}\mathrm{C}$(${\ensuremath{\nu}}_{\mathit{e}}$,${\mathit{e}}^{\mathrm{\ensuremath{-}}}$${)}^{12}$N, has been observed. The flux-weighted total cross section for the exclusive neutrino-induced nuclear transition $^{12}\mathrm{C}$(${\ensuremath{\nu}}_{\mathit{e}}$,${\mathit{e}}^{\mathrm{\ensuremath{-}}}$${)}^{12}$N(g.s.) is [1.05\ifmmode\pm\else\textpm\fi{}0.10(stat)\ifmmode\pm\else\textpm\fi{}0.10(syst)]\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}41}$ ${\mathrm{cm}}^{2}$. The measured cross section and angular distribution d\ensuremath{\sigma}/d\ensuremath{\Omega} are in agreement with theoretical estimates. The inclusive ${\ensuremath{\nu}}_{\mathit{e}}$ $^{12}\mathrm{C}$ reaction rate, which accounted for the majority of all neutrino interactions observed in this experiment, was determined from a detailed fit of energy and angular distributions for the observed electrons. The inclusive $^{12}\mathrm{C}$(${\ensuremath{\nu}}_{\mathit{e}}$,${\mathit{e}}^{\mathrm{\ensuremath{-}}}$)X cross section is measured to be [1.41\ifmmode\pm\else\textpm\fi{}0.23(tot)]\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}41}$ ${\mathrm{cm}}^{2}$. An upper limit for the sum of the $^{13}\mathrm{C}$(${\ensuremath{\nu}}_{\mathit{e}}$,${\mathit{e}}^{\mathrm{\ensuremath{-}}}$)X${+}^{27}$Al(${\ensuremath{\nu}}_{\mathit{e}}$,${\mathit{e}}^{\mathrm{\ensuremath{-}}}$)X inclusive absorption cross sections is presented.