Initial state: mass and collinear divergences
Hello,
I have been simulating e+e- -> gamma gamma processes in QED, possibly adding BSM contributions due to
axion-like particles. so called ALPs.
It is well known that the electron mass regulates the initial-state collinear singularities, while the total cross section is divergent if one neglects the electron mass.
May I ask you how MadGraph handles the initial-state electron masses and related collinear divergence?
In fact, I noticed that, if I run ee->gamma gamma with no cuts, the inclusive cross section is very unstable and unreliable, while
setting cuts, e.g., on photon rapidities leads to sensible results. Therefore, I suspect that mass effects may not be fully
included and one needs to set cuts to avoid the collinear divergence and get reasonable cross sections.
Thanks in advance,
Gennaro
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