Measurements of Ground-Level Muons at Two Geomagnetic Locations

Abstract

We report new measurements of the muon spectra and the muon charge ratio at ground level in the momentum range from 200 MeV͞c to 120 GeV͞c for two different geomagnetic locations. Above 0.9 GeV͞c the absolute spectra measured in the two locations are in good agreement and are about 10% to 15% lower than previous experimental results. At lower momenta the data show latitude dependent geomagnetic effects. These observations are important for the understanding of the observed neutrino anomaly. PACS numbers: 96.40.Tv, 96.40.Kk, 14.60.PqPrecise measurements of the muon energy spectrum and charge ratio at sea level over a wide energy range provide information on the propagation of cosmic rays in the atmosphere. Together with data on the primary cosmic rays, muon measurements can be used as a test to check calculations of atmospheric cascades and neutrino fluxes [1]. These latter calculations are used to interpret the recent re-

Atmospheric neutrino flux supported by recent muon experiments

“…The dashed curves show the results obtained using the original Bartol code and the dotted curves are the results of the CORT+TARGET model (we shall comment them later). Figure 3 shows a comparison of the calculated differential momentum spectra of µ + and µ − with the ground level data obtained in the experiments CAPRICE 94 [41,42] (h = 1000 g/cm 2 , R c = 0.5 GV) and CAPRICE 97 [42] (h = 886 g/cm 2 , R c = 4.2 GV). The detection cone in both experiments was the same as described above.…”

Distributions of secondary muons at sea level from cosmic gamma rays below 10 TeV

“…Energy spectra of muons were recorded by the same experiment at ground (i.e., at an atmospheric depth of 886 g/cm 2 ) [18]. FLUKA results for positive and negative muons are compared to these data in Fig.…”

“…Finally, the ratio of the fluxes of positively and negatively charged muons is compared to CAPRICE data [18] in Fig. 2b.…”

“…A small fraction of muons, however, have their first origin in photonuclear reactions induced by primary or secondary cosmic gamma rays. Several authors have performed analytical or Monte Carlo calculations of the muon flux produced in gamma showers (see references [10][11][12][13][14][15][16][17][18][19][20][21] of [1]). Most of these calculations were one dimensional and all of them referred to gamma energies much larger than 10 TeV.…”

Outstanding Problems in Particle Astrophysics

“…This simple result compares relatively well to various measurements in several energy ranges. The recent data are from CAPRICE (Kremer et al, 1999), L3-Cosmic (Achard et al, 2004) and BESS (Motoki et al, 2003). One can also see the level of relative systematic uncertainties between different measurements.…”