Width in Symbolic Mathematica Code

Yes, you can use this way and take a real part of squared matrix
element in the end.

But width term which appears in numerator of squared matrix element cam
be wrong. In particular because
we need (p^2-m^2 -iwm) for left side of matrix element and (p^2-m^2
+iwm) for right side.
In general there is no good treatment of widths. In numerical
calculations Calchep uses
p^2-m^2 1
   ------------------ for proparator and ----------------
for squared propagator.
(p^2-m^2)^2 + w^2m^2 (p^2-m^2)^2 + w^2m^2

Best
    Alexander Pukhov
PS I'll look once more this evening what can be improved. As I
remember propagator in Math output contains width, but substitution
definition
of propagator ignores this information. It was assumed that the user who
needs width will redefine propagator as he likes.

On 09/19/2017 09:47 PM, Kevin Langhoff wrote:
> New question #658298 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/658298
>
> Hello,
>
> What is the best way to account for massive gauge boson width in symbolic calculations with Mathematica? The file sum_int.m has a function propDen[p_,m_,w_] which doesn't return the correct result if I do the naive transformation to (p^2-m^2 -iwm) because there doesn't seem to be an absolute value used.
>
> Thanks!
>