A search for $\nu_\mu -> \nu_e$ oscillations in the MINOS experiment

The MINOS experiment uses the NuMI neutrino beam to make precision mea- surements of the neutrino mixing parameters. A beam of !μ is produced at Fer- milab. Its energy spectrum is measured near the production point, and again after 735 km at the Soudan Underground Laboratory. By looking for !e appear- ance in the beam, limits can be placed on the as yet unmeasured mixing angle "13. At the far detector (in the Soudan laboratory), 35 !e candidate events are observed with a predicted background of 27±5(stat.)±2(syst.) events: a 1.5# excess. At 90% C.L. this gives an upper limit range of sin2(2"13) < 0.28–0.34 for the normal neutrino mass hierarchy and sin2(2"13) < 0.36–0.42 for the in- verted hierarchy, depending upon the CP-violating phase $CP.