Hello(adsbygoogle = window.adsbygoogle || []).push({});

The Breit-Wigner formula says that the cross section for a resonance is proportional to

[tex]

\frac{1}{(2S_a + 1)(2 S_b + 1)},

[/tex]

where Sa and Sb are the spins of the incident particles. What's the reason for this? I don't understand it because for a general cross section there appears just the inverse of that because that's what enters the density-of-states.

Thanks,

Bruno

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Breit-Wigner formula

**Physics Forums | Science Articles, Homework Help, Discussion**