Cosmic ray muon charge ratio in the MINOS Far Detector.

摘要

The MINOS Far Detector is a 5.4 kiloton (5.2 kt steel plus 0.2 kt scintillator plus aluminum skin) magnetized tracking calorimeter located 710 meters underground in the Soudan mine in Northern Minnesota. MINOS is the first large, deep underground detector with a magnetic field and thus capable of making measurements of the momentum and charge of cosmic ray muons.; Despite encountering unexpected anomalies in distributions of the charge ratio (Nmu+/N mu-) of cosmic muons, a method of cancelling systematic errors is proposed and demonstrated. The result is Reff = 1.346 +/- 0.002 (stat) +/- 0.016 (syst) for the averaged charge ratio; and a result for a rising fit to slant depth of R(X) = 1.300 +/- 0.008 (stat) +/- 0.016 (syst) + (1.8 +/- 0.3) x 10-5 x X, valid over the range of slant depths from 2000 X 6000 MWE. This slant depth range corresponds to minimum surface muon energies between 750 GeV and 5 TeV.