🚀 go-pugleaf

In article <10APR199210204620@deimos.ucc.umass.edu>, s5169180@deimos.ucc.umass.edu (S5169180) writes...
>>Brahm at Caltech wrote :
>>Mass is the pole of the propagator. ...
> 
>I absolutely agree with that argument. Therefore finding mass is same to
>finding bump in the cross section. It has a very useful meaning
>phenomenologically. However it can't give the reason how or why a particle has
>a specific physical(or numerical) value. My question is if we can predict
>masses of quarks or leptons purely in theoretical way, instead of experiments.

Sure.  Check out Physical Review Letters or Physical Review D on any typical
week.  You'll find many theoretical explanations of the mass spectrum of the
quarks and/or leptons.  The problem is that we don't know which, if any, 
are correct explanations.  In the absence of additional experimental evidence
for which theories are correct, it's just speculation.  

By the way,

I would say that the pole of the propagator is the mass, not the other way
around.  You write a wave-equation and solve it for the Green's function.  It
turns out that the propagator has a pole when the particle is on-shell.  I
suppose you could just postulate things in the reverse order, but you don't
learn anything by doing that.  

-Scott