Compute Breit-Wigner for particle decay

1. Feb 5, 2009

mefistofeles

Hey, Im 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 Im 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 [Broken]

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

Last edited by a moderator: May 4, 2017
2. Feb 5, 2009

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.

3. Feb 6, 2009

clem

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

4. Feb 6, 2009

mefistofeles

OK, thats 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.

5. Feb 6, 2009

clem

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