Still Another Conservation Law — Question 10

Question 10

Strangeness conservation is a necessary test rather than a complete mechanism label

Two hypothetical transitions conserve electric charge, baryon number and energy. A changes strangeness by +1. B has Delta S=0. Their amplitudes are not supplied.

1. State what follows about strong and electromagnetic mechanisms for A and B.

2. In a model for B, strong and weak amplitudes are $A_s=1$ and $A_w=.020e^{i\phi}$ in common units. Find the extreme total rate factors relative to $|A_s|^2$.

Question 10 - Solution

Strangeness conservation is a necessary test rather than a complete mechanism label

(a) Method and calculation

$$\boxed{\Delta S_A=+1\Rightarrow A_s=A_{\mathrm{em}}=0}\quad\text{for a strangeness-changing transition}.$$$$\boxed{\Delta S_B=0}\quad\text{does not exclude a weak contribution or guarantee a strong one}.$$

(b) Interpretation and further calculation

$$|A_s+A_w|^2=1+.020^2+.040\cos\phi.$$$$\boxed{R_{\min}=.980^2=.9604,\quad R_{\max}=1.020^2=1.0404}.$$

Physical check

A selection rule can exclude an interaction but cannot by itself determine all allowed amplitudes. Coherent contributions interfere when they connect the same states.