The following is a paper by H. Aspden published in Physics Essays, v. 2, pp. 360-367 (1989).
Abstract: Pion creation is discussed using the same physical principles as those involved in a recent paper [Physics Essays, 1, 72 (1988)] on proton creation. The proton-electron mass ratio was deduced theoretically with part per million concordance with its measured value. Now it is shown that the theory for the charged pion gives a pion/electron mass ratio also in precise accord with its measured value. Other meson creation is discussed and particularly the neutral pion, which is dependent upon resonant interactions that account for its lifetime and mass in a way that supports the proton creation theory.
The full text of this paper may also be seen in PDF format as Paper No. 11 in the author's 1996 book Aether Science Papers which is of record in the author's website http://www.haroldaspden.com.