<< "dirac/Tracer.m"

VectorDimension[4]

Spur[1]

lepton  =  
      G[le, pe]**G[le, {mu}]**G[le,  U  -  G5]**G[le, pnu]**G[le, {nu}]**
        G[le, U  -  G5]

lept  =  lepton /. le -> 1

baryon =  
      G[lp, pp  +  mp U]**G[lp, {mu}]**G[lp,  cvs U  - cas G5]**
        G[lp, pn  +  mn U]**G[lp, {nu}]**G[lp, cv U  -  ca G5]

bary  = Simplify[ baryon /. lp -> 1]

msq  = Gf^2 cost^2/2 Simplify[ ContractEpsGamma[lept bary]]

msq1  = 
      Simplify[ 
        msq /. {pe . pnu -> pcm^2,  pe . pp -> pcm mp, pe . pn -> mn pcm, 
             pnu . pp -> mp pcm,  pnu . pn -> mn pcm}]

width  =  pcm/(8 Pi hbar delta^2) msq1 /. pcm -> delta/2