pp->tt>decay: zero xsection after pdemanding soft b criteria

Hi,

You are probably putting too strong cut for our integrator to be able to integrate such matrix-element.

The only solution that I can see is to hack MadSpin in order to make making such decay with such cut included.

Cheers,

Olivier

> On 7 Apr 2017, at 08:23, shibasipu <email address hidden> wrote:
>
> New question #614512 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/614512
>
> Hi Olivier,
> I am generating the following process.
>> generate p p > t t~ , ( t > w+ b , w+ > l+ vl ) , (t~ > w- b~ , w- > l- vl~)
>
> I am demanding soft b's or b will go through beam line to treat above process as a background for 2l+MET
>
> For soft b, I am applying the following cuts.
> 1. maxm pT of b = 10
> 2. minm eta of b = 5
> 3. minm drbb=0.4, minm drbl=0.4.
>
> But in the end, I am getting following error message.
> Creating Jobs
> INFO: Refine results to 10000
> INFO: Generating 10000.0 unweigthed events.
> INFO: Effective Luminosity 1.2e+103 pb^-1
> INFO: need to improve 0 channels
> Survey return zero cross section.
> Typical reasons are the following:
> 1) A massive s-channel particle has a width set to zero.
> 2) The pdf are zero for at least one of the initial state particles
> or you are using maxjetflavor=4 for initial state b:s.
> 3) The cuts are too strong.
> Please check/correct your param_card and/or your run_card.
> Zero result detected: See https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/FAQ-General-14
>
> Please comment , is there any mistake while applying the cuts on b's.
>
>
>
> Regards,
> Shiba
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

thanks.

>You are probably putting too strong cut for our integrator to be able to integrate such matrix-element.

I think, i have applied only minimal cuts.

>The only solution that I can see is to hack MadSpin in order to make making such decay with such cut included.

Which file should i edit inside Madspin ?

Regards,
Shiba

Hi Olivier,
                    If I relax the cuts for b-quark i.e.

1. maxm pT of b = 20
2. minm eta of b = 2.5
3. minm drbb=0.4, minm drbl=0.4.

and along with lepton cuts

I am getting Xsection of p p > t t~ , ( t > w+ b , w+ > l+ vl ) , (t~ > w- b~ , w- > l- vl~)= 6.4 fb.

Regards,
Shiba

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