Excluding u channel from t channel diagrams

There are two ways

1)  in interactive mode  you can  delete some diagrams.

2)  One can exclude diagrams  which contain virtual particles defined by
the user. This option is available in both interactive and batch modes.

I hope it helps, in spite it is not   exactly that you need.

Best

    Alexander Pukhov

On 14.04.2020 11:33, Shivam Verma wrote:
> Question #689906 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/689906
>
> Description changed to:
> Is there a way in calchep to exclude the u channel diagram contribution
> for the calculation of matrix amplitude (symb1.m) and have just t
> channel contribution?
>

Thank you for the quick reply!

I just had a follow up.
So, If a process (for example a scalar particle scattering with itself) having a t channel diagram with a possible u channel, the squared matrix amplitude that will be calculated using calchep will consider both the possible diagrams and one cannot separate the contribution from a specific channel (t or u) but the ultimate result will be exactly what one might get by solving the matrix amplitude in any other way. Is that so?

Best,
Shivam

CalcHEP calculates squared  diagrams. Among them there are diagrams of
interference  of t and u channel  amplitude diagrams. Thus result is not
presented as a sum of u- and t-channel contributions. Sum of all
squared  diagrams presents correct final result which can be compared
with other ones  and should agree with them.

Best

    Alexander Pukhov

On 15.04.2020 17:17, Shivam Verma wrote:
> Question #689906 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/689906
>
> Status: Answered => Open
>
> Shivam Verma is still having a problem:
> Thank you for the quick reply!
>
> I just had a follow up.
> So, If a process (for example a scalar particle scattering with itself) having a t channel diagram with a possible u channel, the squared matrix amplitude that will be calculated using calchep will consider both the possible diagrams and one cannot separate the contribution from a specific channel (t or u) but the ultimate result will be exactly what one might get by solving the matrix amplitude in any other way. Is that so?
>
> Best,
> Shivam
>

Ok. Thank you Professor Pukhov! That solves my query.