Cosmic ray measurement of the 54Mn beta - partial half-life.

Abstract

In the fully stripped cosmic rays, the electron capture decay of {sup 54}Mn ({tau}{sub 1/2}=312{ital d}) is strongly suppressed. In this situation the {beta}{sup {minus}} decay channel dominates; however, this half-life has never been measured in the laboratory. Some lower limits have been placed on it previously. Using the cosmic-ray data from the Ulysses spacecraft high-energy telescope (HET) and a self-consistent model of the galactic transport of cosmic rays, this partial lifetime can be determined. The best-fit {beta}{sup {minus}} partial decay lifetime is dependent on the interstellar gas density, but is constrained to be between 1{endash}2{times}10{sup 6} yr. This is consistent with, but much more restrictive than, earlier limits placed on the lifetime ({approx_gt}3{times}10{sup 4} and {approx_gt}2.95{times}10{sup 5} yr) from direct and indirect methods, respectively. This determination using the cosmic-ray data requires laboratory verification for which there appears to be interest. {copyright} {ital 1996 The American Physical Society.}