five-flavour scheme

Asked by niujj on 2015-11-24

In the param_card.dat of my generate process file,there is a MT parameter ,but from the link below there is not in the five-flavour but in the four-flavour scheme.
 link :http://amcatnlo.web.cern.ch/amcatnlo/cards_paper.htm

I thought there is a problem in the definition of proton.
How to define p for p p collision in the five-flavour scheme?

Question information

Language:
English Edit question
Status:
Open
For:
MadGraph5_aMC@NLO Edit question
Assignee:
Paolo Torrielli Edit question
Last query:
2015-11-26
Last reply:
2015-11-25
niujj (501852601-j) said : #1

I thought it is in the four-flavour scheme in default, how to change it?

In 2.3.3, you just need to import a model in 5flavor.

for example
import model sm-no_b_mass

and automatically the p/j definition will be in five flavor.

alternatively you can change the p/j definition by using
define p = p b b~
define j = p

Note that using a 4 flavor model and setting the b mass to zero in the param_card is not efficient compare to using a 5 flavor model.

Cheers,

Olivier

> On Nov 24, 2015, at 22:08, 牛娟娟 <email address hidden> wrote:
>
> Question #275390 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/275390
>
> 牛娟娟 posted a new comment:
> I thought it is in the four-flavour scheme in default, how to change it?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

niujj (501852601-j) said : #3

Thank you so much for the reply.
There are still some questions. I use the model sm-no_b_mass, and the parameters are followed as the link above http://amcatnlo.web.cern.ch/amcatnlo/cards_paper.htm.
But the result is not match for the process a.1 in page 74 of the jhep (1405.0301v2).
his LO 1.375 NLO 1.773
mine LO 2.646 NLO 3.528
What's wrong for the big difference?

Hello,
I don't precisely know what causes the discrepancy, but I run this process with version 2.3.4,
default cards, and got results compatible with the table of 1405.0301.
You could try and do the same as I did, and afterwards, compare the new cards (i.e. the defaults
in 2.3.4) with the old ones (i.e. the ones you used to get the numbers you quoted above), to pin
down the setting that causes the difference.
Cheers.
Paolo

niujj (501852601-j) said : #5

hello ,Paolo
I just do as you told me ,but I couldn't find the version 2.3.4 on the net .Could't you tell me where I can find it?
However I also try it with version 2.3.3,default cards.(default beam energy is 6500 Gev).
The result is LO 1.352 NLO 1.736
But the beam energy of the table in 1405.0301 is 13 TeV , Then I change the card,
and the result is LO 2.555 NLO 3.414
Is that the same as you?
The second problem is that the same process I tried two times, but the results are different
first time : LO 2.555 NLO 3.414
second time : LO 2.565 NLO 3.4146
Why?

Cheers,
niujj

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