Precise Measurements of Atmospheric Muon Fluxes with the BESS Spectrometer

Abstract

The vertical absolute fluxes of atmospheric muons and muon charge ratio have been measured precisely at different geomagnetic locations by using the BESS spectrometer. The observations had been performed at sea level (30 m above sea level) in Tsukuba, Japan, and at 360 m above sea level in Lynn Lake, Canada. The vertical cutoff rigidities in Tsukuba (36.2 N, 140.1 E) and in Lynn Lake (56.5 N, 101.0 W) are 11.4 GV and 0.4 GV, respectively. We have obtained vertical fluxes of positive and negative muons in a momentum range from 0.6 to 20 GeV/c with systematic errors less than 3 % in both measurements. By comparing the data collected at two different geomagnetic latitudes, we have seen an effect of cutoff rigidity. The dependence on the atmospheric pressure and temperature, and the solar modulation effect have been also clearly observed. We also clearly observed the decrease of charge ratio of muons at low momentum side with at higher cutoff rigidity region.

35 pages, 9 figures. Submitted to Astroparticle Physics

References in corpus (8)

• Evidence for oscillation of atmospheric neutrinos
• Precise Measurement of Cosmic-Ray Proton and Helium Spectra with the BESS Spectrometer
• Calculation of the Flux of Atmospheric Neutrinos
• Protons in near earth orbit
• Measurements of Cosmic-ray Low-energy Antiproton and Proton Spectra in a Transient Period of the Solar Field Reversal
• Comparison of Atmospheric Neutrino Flux Calculations at Low Energies
• Development of a Large-Area Aerogel Cherenkov Counter Onboard BESS
• Large-Area Scintillator Hodoscope with 50 ps Timing Resolution Onboard BESS

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