Compute Breit-Wigner for particle decay

[mefistofeles]

Hey, I am just woondering if anyone here have computed (numerically) the Breit-Wigner for a particle decay. I have to do some nonlinear fitting of data but I need to compute this, any ideas?

My case is specific, and I am brand new to particle physics, it's for a tau decay into Kaon, pion and tau neutrino. The expression I have for the Breit-Wigner is posted in: http://mathbin.net/5566

I still don't understand the math beneath the expression. All I am asked is to compute it, what I am having trouble with is that i on the Breit-Wigner, I am not sure if that's the imaginary unit or something different, so if you know please help me compute this. Thanks for the attention.

 

[mefistofeles]

OK I gave it a second thought and I got it, that BW (for that decay) appears inside a function which is squared, so the imaginary part actually disappears, should have seen this before posting heh, sorry.

 

[Meir Achuz]

The I am doesn't disappear, but gets squared in the denominator.

 

[mefistofeles]

OK, that's what I meant by "disappear", sorry the non-technical term. And you are right, it gets squared so that i^2 = -1 and the final result is real which corresponds to the "magnitude" of the complex number.

 

[Meir Achuz]

No. You take the complex conjugate so (i)(-i)=+1.