Meson cascade in the atmosphere, uncertainties in calculating the fluxes of high-energy muons, and data of direct measur
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EMENTARY PARTICLES AND FIELDS Experiment
Meson Cascade in the Atmosphere, Uncertainties in Calculating the Fluxes of High-Energy Muons, and Data of Direct Measurements A. A. Kochanov* , T. S. Sinegovskaya, and S. I. Sinegovsky** Irkutsk State University, Irkutsk, Russia Received December 25, 2006; in final form, April 17, 2007
Abstract—A new calculation of the atmospheric fluxes of cosmic-ray hadrons and muons in the energy range 10−104 GeV is performed on the basis of the method for solving nuclear-cascade equations with allowance for a nonscaling behavior of inclusive hadron-production cross sections, the growth of cross sections for inelastic hadron–nucleus collisions with increasing energy, and a non-power-law character of the primary spectrum. The fluxes of secondary cosmic rays at various levels in the atmosphere are calculated for three models of the spectrum and composition of primary cosmic rays. The effect of uncertainties in the spectrum and composition of primary cosmic rays on the flux of atmospheric muons and their charge ratio at sea level is investigated. The calculated energy spectra of muons at sea level are compared with the results of previous experiments and the results of recent measurements performed by means of the L3 + Cosmic and CosmoALEPH spectrometers, as well as with the results of other calculations. PACS numbers: 13.85.Tp, 95.85.Ry, 96.50.Sb DOI: 10.1134/S1063778807110117
1. INTRODUCTION A comparison of the calculated spectra and zenithangle distributions of atmospheric muons with the results of respective measurements makes it possible to solve problems of two types: (i) those that are associated with studying hadron–nucleus interactions for a known energy spectrum and a known composition of primary cosmic rays and (ii) those that are associated with indirectly studying the properties of primary cosmic rays for a given hadron-production model. Procedures for calculating atmospheric-muon fluxes have undergone substantial changes in recent years. This is likely to be motivated by new direct measurements of the spectrum and composition of primary cosmic rays rather than by refinement of hadron-interaction models. Despite a vigorous development of numerical methods for solving transport equations for cosmic-ray particles in the atmosphere, the creation of new codes for Monte Carlo simulations, and some kind of unification of computational procedures, sizable distinctions between predictions for the atmospheric-muon flux remain even if use is made of the same code. In the present study, we perform a new calculation of hadron fluxes and vertical muon fluxes at various levels in the atmosphere for energies in the * **
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range 10−104 GeV. As input data in these calculations, we employ various parametrizations of the spectrum and composition of primary cosmic rays [1– 3]. The calculations are based on the method that was originally developed for solving problems of neutrino transport in matter [4] and which was then modified to apply it to the tr
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