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

Ive come across some approximate cross section formulas during a course of particle physics. And in a reaction like

A + B --> R --> C + D

the cross section should be something like

[tex]

\sigma = K\frac{\Gamma_R^{AB}\Gamma_R^{CD}}{(s-m_R^2)^2+m_R^2\Gamma_R^2}

[/tex]

Where K is a constant (depending on spin and color multiplicity), s is the center of mass energy sqared, m is the mass, and Gamma is the width calculated from

[tex]

\Gamma_R^{CD} = \bar{\abs{M}^2}\frac{P_C}{8\pi m_R^2}

[/tex]

My question is now how to handle a situation when the intermediate particle is mass less. Say a photon or a gluon. Can I take them as being virtual and thus having a mass which should be equal to the CM energy?

Greatfull if anyone can shed some light on this.

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

Dismiss Notice

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!

# Approximate cross section calculations

Loading...

Similar Threads for Approximate cross section |
---|

A Question about a cross section from PDG |

I E+e- cross-section |

I Antiproton flux and cross-sections in antideuterium production |

A Fiducial Cross Section |

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