Muons in air showers at the Pierre Auger Observatory: mean number in highly inclined events.

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

PHYSICAL REVIEW D

AMER PHYSICAL SOC

Lugar: New York; Año: 2015 vol. 91 p. 32003 - 32003

1550-7998

We present the first hybrid measurement of the average muon number in air showers at ultrahighenergies, initiated by cosmic rays with zenith angles between 62° and 80°. The measurement is based on174 hybrid events recorded simultaneously with the surface detector array and the fluorescence detector ofthe Pierre Auger Observatory. The muon number for each shower is derived by scaling a simulatedreference profile of the lateral muon density distribution at the ground until it fits the data. A 1019 eVshower with a zenith angle of 67°, which arrives at the surface detector array at an altitude of 1450 mabove sea level, contains on average ð2.68 0.04 0.48ðsysÞÞ × 107 muons with energies larger than0.3 GeV. The logarithmic gain d lnNμ=d lnE of muons with increasing energy between 4 × 1018 eV and5 × 1019 eV is measured to be ð1.029 0.024 0.030ðsysÞÞ.