MadGraph5_aMC@NLO

Difference between 1.5.12 and 2.1.0

Asked by teddym

Hi:
   I'm using MadGraph version 2.1.0 to generate event, and one of my friends is using MadGraph version 1.5.12( or maybe 1.5.13). There are several problems when we check the same process with the same cuts.

we are using the same param_card and pythia_card and delphes_card.

1. For the process p p > t t~ w, -> b b~ j j j j l vl (only one lepton)
    if we both choose "F" for fix_ren_scale and fix_fac_scale, (other parameters in run card are the same)
    we get different CS: 2.1.0: ~110fb
                                  1.5.12: ~127fb
    but if we both choose "T" for fix_ren_scale and fix_fac_scale and use M_Z as the scale
   we get the same CS: ~177fb
    ( is there any difference in the default scale choice? )

2. For the same process as above,
    using the same cuts, the cuts efficiency is different at the final step,
    for 2.1.0: using F fix_ren_scale and fix_fac_scale
        1.5.12: using fixed scale at M_Z
   (The scale would affect the distribution? )

3. For the process p p > t t~, -> b b j j l vl ( only one lepton )
    we all choose "F" for fix_ren_scale and fix_fac_scale:
    we get the same CS
    ( seems the default scale in different version do not affect the CS, contrary to 1)
    But the Cuts efficiency after the same cuts is different. The result from 2.1.0 is 2 times that from 1.5.12
    ( Why? all the cards are the same )

4. For the process p p > t t~ Z, -> ( One lepton final states )
    We all choose "T" for fix_ren_scale and fix_fac_scale
    but for 2.1.0: scale: M_top
          for 1.5.12: scale: M_Z
    we get different CS ( which make sense ), and We get almost the same Cuts efficiency after the same cuts.
    ( Seems that scale do not affect the distribution, contrary to 2 )

So I want to know that what is the difference between different version of MadGraph that leads to such things.

Thanks very much

Question information

Language:
English Edit question
Status:
Answered
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Last query:
Last reply:
Revision history for this message
teddym (niepanchongsheng) said : 		#1

The Cuts we've used are some basic cuts ( according ATLAS papers) and MET > 200, HT > 500, MT> 150 Nj >=4, Nb>=2 ( in this order )
For ttw process, the difference between two cuts efficiency is within 10%~20% from basic cut to HT> 500 ( which is acceptable ) from MT>150, the difference is larger than about 50% and at last the efficiency from 2.1.0 is two times that from 1.5.12

For tt~ process, the difference become prominent only after Nb>=2 Cuts.

Thanks

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#2

Hi Teddym,

Indeed, the function used for the determination of the dynamical scale was change between 1.5.15 and 2.0.0.
The main change is not include anymore the jet coming from w/z/t decay in the clustering algorithm which determine the factorization/renormalization scale
of the process.

Cheers,

Olivier

On Sep 26, 2014, at 7:23 AM, teddym <email address hidden> wrote:

> Question #255027 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/255027
>
> teddym gave more information on the question:
> The Cuts we've used are some basic cuts ( according ATLAS papers) and MET > 200, HT > 500, MT> 150 Nj >=4, Nb>=2 ( in this order )
> For ttw process, the difference between two cuts efficiency is within 10%~20% from basic cut to HT> 500 ( which is acceptable ) from MT>150, the difference is larger than about 50% and at last the efficiency from 2.1.0 is two times that from 1.5.12
>
> For tt~ process, the difference become prominent only after Nb>=2 Cuts.
>
> Thanks
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
teddym (niepanchongsheng) said : 		#3

Hi Olivier:
     Thanks!
> The main change is not include anymore the jet coming from w/z/t decay in the clustering algorithm which determine the
> factorization/renormalization scaleof the process.

     I'm a little confused about this, if not include anmore jets from w/z/t decay, then, how the program determine the scale of process p p > t t~ and p p > t t~ w ? ( Since all using default dynamical scale, different version give different CS for ttw process but the same CS for tt process)

Best!

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#4

Hi,

The difference for tt~W should be linked to a second change in the formula for the factorisation scale.
in the previous version one of the factorization scale was just the transverse mass of the W (since the W particle breaks the beam).
This was proven to be sometimes too soft, so now we take the geometrical average between the transverse mass of the W and the transverse mass of the top system.

Cheers,

Olivier

On Sep 28, 2014, at 3:06 AM, teddym <email address hidden> wrote:

> Question #255027 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/255027
>
> Status: Answered => Open
>
> teddym is still having a problem:
> Hi Olivier:
> Thanks!
>> The main change is not include anymore the jet coming from w/z/t decay in the clustering algorithm which determine the
>> factorization/renormalization scaleof the process.
>
> I'm a little confused about this, if not include anmore jets from w/z/t decay, then, how the program determine the scale of process p p > t t~ and p p > t t~ w ? ( Since all using default dynamical scale, different version give different CS for ttw process but the same CS for tt process)
>
> Best!
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
teddym (niepanchongsheng) said : 		#5

Hi:
   Thanks for your reply!
   I have another question.
   How could I pick the dynamical scale ( ren_scale and fac_scale) for each event from MadGraph?

Best!

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said : 		#6

Hi,

Those information are not part of the LHE convention.
To have access to them, you can use the syscalc interface.
(you have to set the use_syst = T in the run_card)
and then each event will have additional information including the renormalization and factorization scale.

The detail on the additional format is in this webpage https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/SysCalc
(under the technical details part)

Cheers,

Olivier
On Oct 2, 2014, at 9:01 AM, teddym <email address hidden> wrote:

> Question #255027 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/255027
>
> Status: Answered => Open
>
> teddym is still having a problem:
> Hi:
> Thanks for your reply!
> I have another question.
> How could I pick the dynamical scale ( ren_scale and fac_scale) for each event from MadGraph?
>
> Best!
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Can you help with this problem?

Provide an answer of your own, or ask teddym for more information if necessary.

To post a message you must log in.