Science Record

36

All the decay processes given in (1) are the results of the joint effect of the strong as well as the weak interaction. The strong interaction chosen in this note is the isotopic invariant Hamiltonian suggested by Salam e al.& 4 The forms of the Hamiltonian are

H, = Niy,t-7N, H,= Miy,n-S+3-niy;A°,

H; = i[3 X x]iy;3,

H,= Fiyst-28, G) H,= Niy;K 4+ AMiy;,K*N,

He= Niyst-SK + K*2-tiy;N,

H, = Miy,Kin& — FinK*iy,,

i

Hy = Biyst:imK*S — Siy;Kit, tt.

The above Hamiltonian is”slightly different from that proposed by Salam. In our case, the coupling of K-meson to nucleon and hyperons involves y;, which is different from the corresponding expression in Salam’s Hamiltonian. H, and H, are also slightly modified in order to guarantee the invariance under time reversal.

The lowest order approximation of the perturbation theory is used. The closed polygons in the Feynman diagrams of the Kt-meson and the hyperon decays make the corresponding S-matrix elements diverge logarithmically.

2

A cut-off factor is thus introduced to cut-off the divergent part of

A PER the integral. The absolute life times obtained can hardly be trusted, as in our calculation the perturbation theory with a cutoff is used. The mean life time ratio and the branching ratios of different decay modes are thus

discussed and compared with the experimental results.

The Feynman diagrams of Kt-meson decay can be easily written down. However, two points need to be considered while discussing the hyperon decay, as the weak interactions involved are those between two pairs of heavy particles.

I. Experiments show that in the decay of strange particles, the change of the strangeness quantum number can be +1 only. In order to exclude the possibility of the strangeness quantum number changing by two units in the decay processes, the pair of charged particles and neutral particles must be chosen in such a way that AQ= AS, The pairs of baryons satisfying this condition are the following: