Composition and spectra of cosmic-ray hadrons at sea level

Abstract

Energy spectra of neutrons, protons and pions were measured at sea level using a cosmic-ray hadron spectrometer consisting of a double neutron monitor and scintillation counters. All the hadron spectra were determined simultaneously. The analysis of the observed neutron multiplicity distributions was based on computer simulations of hadron cascades in the spectrometer. The neutron spectrum was determined in the range 0.05-1000 GeV. The proton-to-neutron ratio was estimated below 2 GeV, where the contribution of pions is of minor importance. Assuming a smooth rise of the p/n ratio above 2 GeV to a constant value at 5 GeV, the pion spectrum was determined between 2 and 50 GeV. At higher energies, where accompanied hadrons distort the measured spectra, upper bounds of the pion intensities were estimated. The composition of the hadron flux at sea level is discussed on the basis of the present and previous experimental and theoretical results.