A measurement of the atmospheric muon charge ratio between 50 and 400 GeV using the MINOS Near Detector

The torroidally magnetized MINOS Near Detector is located at Fermilab at the end of the NuMI beam line. It is situated at 133.5 meters above sea level with a vertical overburden of 224.6 meters of water equivalent. The detector has collected charge seperated atmospheric muons for a minimum of 37 days in both the forward and reversed B-field directions. Combining equal periods of forward and reversed field data, almost 40 million muons per sample, reduces the systematic effects of geometric acceptance due to the magnetic field and an asymmetric detector. This data set allows an accurate measurement of the atmospheric muon charge ratio between 50 and 400 GeV to be performed.