On the masses and modes of decay of heavy mesons produced by cosmic radiation

Abstract

A large emulsion stack, exposed at high altitude, has been used to study the decaymodes of K-particles which produce a single charged secondary. The 5 decay modes, K μ, χ, κ and τ' have been recognized from the nature and energy of the charged secondary. The masses of the parent particles of the two-body decay modes, K μ and χ found from the mean range of the charged secondary are (976±7) me and (969±3) me respectively. Independent values derived from measurements of the scattering of the secondary track near the decay point are (954±17) me and (972±15) me respectively. The reliability of these mass values is discussed. An examination of the relative frequency of the decay modes in these experimental conditions indicates that the K μ -and χ-modes constitute respectively about 67 % and 20 % of all the K-particle decays: the Kβ, κ- and τ'-modes being present to about 9 %, 3 %, and 1 % respectively.