Cross section for W+c in Madgraph

Hi,

I’m confused about your setup which is a mix of three and five flavour.
This does not make any sense to me.

Cheers,

Olivier

> On 3 Mar 2017, at 15:33, Paolo Gunnellini <email address hidden> wrote:
>
> New question #521970 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/521970
>
> Dear Madgraph authors,
>
> we have a question concerning a LO W+c sample, with up to three additional partons included in the calculation, we tried to generate.
>
> The cards we used can be found at the following link:
>
> http://pgunnell.web.cern.ch/pgunnell/WC-cards/
>
> We want to go to very low pT of the charm and we set a very low cut on the selected jets (10 MeV) at the card level.
> A very first question is: is that fine or is it too low?
>
> What it is observed is that the cross section after matching with Pythia8 is very different with respect to an inclusive sample (and with respect to first comparisons with data) and we were wondering if we are doing something wrong with the generation. Could we ask you to have a look at the cards and let us know if you see any bug? We suspect that this might be due to the low pT we apply to the final-state jets..
>
> Looking forward to your reply, we thank you in advance.
>
> Best regards,
>
> Paolo Gunnellini
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Dear Olivier.

thanks a lot for your reply..could you point us what we should change to have the correct generation for this particular process, please?

Thanks a lot in advance.

(I updated the proc_card, since there was a little bug before, coming from some debugging)

Best regards,

Paolo Gunnellini

Hi,

> could you point us what we should change to
> have the correct generation for this particular process, please?

Please do not trust blindly what I will propose to you. You are obviously responsible for your own genration

But your proc_card should be something like:

define p = p / c c~
define j = p
define cquark = c c~
define ell+ = mu+
define ell- = mu-
generate p p > w+ cquark, w+ > ell+ vl / h @0
add process p p > w+ cquark j, w+ > ell+ vl / h @1
add process p p > w+ cquark j j, w+ > ell+ vl / h @2
add process p p > w- cquark, w- > ell- vl~ / h @3
add process p p > w- cquark j, w- > ell- vl~ / h @4
add process p p > w- cquark j j, w- > ell- vl~ / h @5
output WCJetsToMuNu_3f_LO_MLM -nojpeg

I.e. you should not have c/b quark in the initial/final state.

In top of that, you should also ensure that your model has a massive c and b quark (at the model level).

In your run_card you should also set
asrwgtflavor to 3
And ensure that your Parton-shower is also on three flavour.
They might need more but that’s all that I have spotted quickly.
Cheers,

Olivier

PS: Note that your ptj is actually not used since you have set:
  True = auto_ptj_mjj ! Automatic setting of ptj and mjj
And therefore your value of ptj is automatically set to xqcut.
(Setting a value lower than xqcut is basically meaningless since your jet will be veto by xqcut anyway).

> On 3 Mar 2017, at 16:13, Paolo Gunnellini <email address hidden> wrote:
>
> Question #521970 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/521970
>
> Status: Answered => Open
>
> Paolo Gunnellini is still having a problem:
> Dear Olivier.
>
> thanks a lot for your reply..could you point us what we should change to
> have the correct generation for this particular process, please?
>
> Thanks a lot in advance.
>
> (I updated the proc_card, since there was a little bug before, coming
> from some debugging)
>
> Best regards,
>
> Paolo Gunnellini
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.