Non renormalisable operators

Surely. No problem.
You can find examples in

https://hepmdb.soton.ac.uk/

Best
    Alexander Pukhov

On 03/15/2017 06:58 PM, Teto wrote:
> Question #557115 on CalcHEP changed:
> https://answers.launchpad.net/calchep/+question/557115
>
> Summary changed to:
> Non renormalisable operators
>
> Description changed to:
> Is it possible to inizialise a model file with a non renormalisable
> operator (dim 5) ?
>

No, you just need cuts to calculate a physically meaningful
quantity. It could be cuts for small energy and small radiation angle.

Divergent tree level formulas indeed dive correct LO result. But
their direct treatment is not right. In QED they give a small
cross section of
production of large number of photos, but not large cross section of
production of one photon. It formally solved by loop consideration.

It is a generic problem for both normalizable and non-normalizable
interaction.

Best
    Alexander Pukhov

On 03/13/2017 08:37 PM, Teto wrote:
> New question #557115 on CalcHEP:
> https://answers.launchpad.net/calchep/+question/557115
>
> Hi,
>
> I'd like to use CalcHEP to evaluate a 2 to 3 cross section for bremsstrahlung process, but I found myself stuck because this observable is by itself divergent. Contribution from loops and counterterms are needed in order to define a physically meaningful quantity. Nevertheless what I am interested in are the different features in the full theory against an EFT approach, therefore what I'd like calculate is the difference between the matrix element squared in the full theory and in the EFT, then integrated via Monte Carlo over the same 3B phase space. I already know this quantity is well defined and finite. In particular, I need the LHE file to feed to PYTHIA. Therefore here come my questions:
>
> 1) Is it possible to inizialize a model file with a non renormalizable operator ( dim 5) ? I'd like to "cheat" and construct a model where both the full theory and the EFT are defined, such that I can calculate the aforementioned cross section.
> 2) In case (1) works, how can I prevent calcHEP from building squared diagrams for the 2 to 3 body process in which the full theory and the EFT are mixed ? In other words, can I switch of some of the squared diagrams by hand ?
>
> I am sorry for trying to force CalcHEP into something it was probably not meant to be used for,
> and many thanks in advance for your answer
>