is "sigma*v" the thermal cross section?

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Sorry, I  did not see  your mail or forgot to replay.

sigma*v is just  (cross section * velocity) where velocity is a relative
velocity.

For relic density calculation one needs  sigma*v averaged over momentum
distribution caused by finite temperature.

If sigma*v does not depend on momentum in region p^2/M/2<T then thermal
averaging   gives the same v*sigma that you see in CalcHEP.

I use  v*sigma plot to check that   v*sigma indeed is a finite constant
at small p and to find at which p non linear terms appear.

Best

    Alexander Pukhov

On 22.06.2019 0:31, Marco Arroyo-Ureña wrote:
> New question #681530 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/681530
>
> Dear experts
> am evaluate different processes in calchep with a model that contains a Dark Matter candidate. I observe that calchep have an option called "sigma*v". Is "sigma*v" the thermal cross section? Thanks for advance.
>

Dear Alexander Pukhov,
Thank you very much, my question was resolved.
Marco Arroyo

the problem was actually solved