p p > t t~ Xsection when b is included in p

Hi,

This is because, in the first case, the b is not consider as a jet and therefore cut like ptj does not apply on the b-jet.
While in the second case, the b is consider as a jet and therefore the ptj is applied on the b-jet.

Cheers,

Olivier
> On 21 Apr 2017, at 12:14, shibasipu <email address hidden> wrote:
>
> New question #625452 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/625452
>
> Hi Olivier,
> I was comparing below processes in MG5 with and without including b in p.
>
> 1. p p > t t~ with t decaying leptonically : Xsection(14 TeV) = 20.54 pb
> 2. Once you include b in p , Xsection of the above one = 17.36 pb
> (Note: For both the cases, "Cut_decays=T" used in the run_card.dat.)
>
> why the second one less Xsection ? Please clarify.
>
> I have also checked the production Xsection.
> 1. p p > t t~ : xsection(at 14 Tev) = 597.5 pb
> 2. once b included in p : xsection = 598.3 fb
>
> The production xsection is ok.
>
>
> Regards,
> Shiba
>
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,
                   thanks. just to clarify myself :

i. when one starts with inbuilt definition of p, by default in the run_card.dat ," 4 = maxjetflavor ! Maximum jet pdg code" used.
ii. But when starts with definition "p = p b b~", by default in the run_card.dat, " 5 = maxjetflavor ! Maximum jet pdg code" used.

That's why in the second case b is treated as same footing with other light jets as a whole ptj is applied on the b-jet. Is it correct ?

Regards,
Shiba

Hi Olivier,
                    Please clarify the above confusion. Apart from the above one, I have another thing to know.

Suppose I have considered, p = p b b~ and generating the following process.

>generate p p > t t~ QED<=99, ( t > w+ b , w+ > l+ vl ) , ( t~ > w- b~ , w- > l- vl~ )

Now I want to demand soft b criteria in the run_card.dat. Shall I use cuts on j or cuts on b ?

Regards,
Shiba

Hi,

This depend of the maxjetflavor parameter of the run_card.
This defines how the cut on the b quark are applied.

The default for 5-flavor computation is to use the same cut on the b-quark as all the other quark (since they are not distinguishable)
While the default for 4-flavor computation is to have different cut (and therefore use ptb and equivalent on the b-quark)

Cheers,

Olivier

> On 24 Apr 2017, at 07:44, shibasipu <email address hidden> wrote:
>
> Question #625452 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/625452
>
> shibasipu gave more information on the question:
> Hi Olivier,
> Please clarify the above confusion. Apart from the above one, I have another thing to know.
>
> Suppose I have considered, p = p b b~ and generating the following
> process.
>
>> generate p p > t t~ QED<=99, ( t > w+ b , w+ > l+ vl ) , ( t~ > w- b~ ,
> w- > l- vl~ )
>
> Now I want to demand soft b criteria in the run_card.dat. Shall I use
> cuts on j or cuts on b ?
>
>
> Regards,
> Shiba
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,
                      thanks a lot.

>The default for 5-flavor computation is to use the same cut on the b-quark as all the other quark (since they are not distinguishable)
That means, for 5-flavor computation, no need to use ptb and equivalent on the b-quark for soft b's. ptj and equivalent cut on the j
will be sufficient for soft b stuff. Is not it ?

Regards,
Shiba

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