Breit-Wigner formula derivation

[Stickybees]

Does anyone know where this forumula comes from?

http://iopscience.iop.org/0067-0049/134/1/151/fulltext/

I don't quite understand the resonance widths, it's probably a naive question but what is 'resonating' in this context?

Thanks!

 

[mathman]

I know nothing about this material. However, looking at the formula, it looks like E is resonating around E_R.

 

[the_wolfman]

Much like electron orbitals, the nucleons (protons and neutrons) in an atom have discrete energy states. When you have an interaction between an nucleus and an incident particle (proton or neutron for example), the probability that the incident particle will be absorbed is greatly increased if its energy resonates with the energy state of the product (or intermediate) nucleus. The Breit-Wigner formula describes this interaction for certain types of resonances. These resonances have a finite width in energy.