Negative Meson Absorption in Liquid Hydrogen

A theoretical study has been made of the atomic processes involved in the absorption of π^- and K^- mesons in liquid hydrogen, with the main purpose of setting an upper limit on the fraction of K mesons that react with the proton from the P state. The principal mode of de-excitation of the mesonic atom, Auger ionization of neighboring hydrogen atoms, was calculated in Born approximation for all the appropriate initial and final values of n. The Stark mixing process discussed by Day, Snow, and Sucher, which allows S-state reaction from high n orbitals, was calculated quantitatively using an impact parameter method and including the effect of the S-state energy shift. In agreement with Day et al., it was found that practically all of the K^- mesons react from the S state; the actual fraction of P-state reactions is less than 1%. In addition, the calculated cascade time for π^- in liquid hydrogen is compatible with the experimental value.