# Yukawa's Potential

1. Feb 3, 2009

### Ayame17

This may seem like a really obvious question to those that know it but...

We looked at Yukawa's potential the other day, in the form $$W(r)=\frac{\alpha}{r}*e^{-Kr}$$, but our lecturer never explained what K and $$\alpha$$ actually are! I've looked on the net and all I can find is that they are constants. What does they actually stand for?

2. Feb 3, 2009

### nicksauce

Roughly speaking, alpha is a constant representing the "strength" of the force... for the EM force it would be the fine structure constant. K is a constant representing the inverse of the range of the force $R\approx \frac{\hbar}{Mc}$. (M is the mass of the mediating boson). For the EM force R would be infinite, so K would be 0.

Ref: Particle Physics, Martin and Shaw, 3rd Ed.

3. Feb 3, 2009

### Ayame17

Ah, now that makes a lot of sense! Thanks very much!