MadGraph5_aMC@NLO

changing some parameter to external lead unexpected cross section

Asked by Li

Hi,
  I change the FeynRule's internal parameter lam , the Higgs self coupling , to external , and use this UFO in the MadGraph. For example, I run the process e+ e- > z z , and I define the lam = 0.129 ( the SM value ) and change the decay width in the param_card.dat to "auto" then, I got the corss section, for 250GeVx250GeV, 397.4 fb while using SM I get 416.3 fb for the same energy . Since I just change lam from internal parameter to an external parameter and give it's SM value , the difference between this two results confuse me . Can you explain this and tell me how to get change the internal parameter correct?

Best,
Li

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Olivier Mattelaer
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Li (huangli-itp) said : 		#1

maybe these messages are useful, the param_card.inc for the two cases, I don't know why some parameters change, like AEWM1 ,I didn't change it in the param_card.dat.

AEWM1 = 1.325070D+02
      MDL_GF = 1.166390D-05
      AS = 1.180000D-01
      MDL_YMB = 4.700000D+00
      MDL_YMT = 1.730000D+02
      MDL_YMTAU = 1.777000D+00
      MDL_MZ = 9.118800D+01
      MDL_MT = 1.730000D+02
      MDL_MB = 4.700000D+00
      MDL_MH = 1.250000D+02
      MDL_MTA = 1.777000D+00
      MDL_WZ = 2.441404D+00
      MDL_WW = 2.047600D+00
      MDL_WT = 1.491500D+00
      MDL_WH = 6.382339D-03

      AEWM1 = 1.279000D+02
      MDL_GF = 1.166370D-05
      AS = 1.184000D-01
      MDL_YMB = 4.700000D+00
      MDL_YMT = 1.720000D+02
      MDL_YMTAU = 1.777000D+00
      MDL_LAM = 1.289690D-01
      MDL_MZ = 9.118760D+01
      MDL_MTA = 1.777000D+00
      MDL_MT = 1.720000D+02
      MDL_MB = 4.700000D+00
      MDL_MH = 1.250000D+02
      MDL_WZ = 2.411888D+00
      MDL_WW = 2.002780D+00
      MDL_WT = 1.466877D+00
      MDL_WH = 6.526765D-03

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

Hi,

1) Did you double check that your param_card are identical?
2) Did you remove the decay.py?

Cheers,

Olivier

> On Nov 10, 2015, at 04:57, Li <email address hidden> wrote:
>
> Question #273990 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/273990
>
> Li gave more information on the question:
> maybe these messages are useful, the param_card.inc for the two cases, I
> don't know why some parameters change, like AEWM1 ,I didn't change it in
> the param_card.dat.
>
> AEWM1 = 1.325070D+02
> MDL_GF = 1.166390D-05
> AS = 1.180000D-01
> MDL_YMB = 4.700000D+00
> MDL_YMT = 1.730000D+02
> MDL_YMTAU = 1.777000D+00
> MDL_MZ = 9.118800D+01
> MDL_MT = 1.730000D+02
> MDL_MB = 4.700000D+00
> MDL_MH = 1.250000D+02
> MDL_MTA = 1.777000D+00
> MDL_WZ = 2.441404D+00
> MDL_WW = 2.047600D+00
> MDL_WT = 1.491500D+00
> MDL_WH = 6.382339D-03
>
>
>
> AEWM1 = 1.279000D+02
> MDL_GF = 1.166370D-05
> AS = 1.184000D-01
> MDL_YMB = 4.700000D+00
> MDL_YMT = 1.720000D+02
> MDL_YMTAU = 1.777000D+00
> MDL_LAM = 1.289690D-01
> MDL_MZ = 9.118760D+01
> MDL_MTA = 1.777000D+00
> MDL_MT = 1.720000D+02
> MDL_MB = 4.700000D+00
> MDL_MH = 1.250000D+02
> MDL_WZ = 2.411888D+00
> MDL_WW = 2.002780D+00
> MDL_WT = 1.466877D+00
> MDL_WH = 6.526765D-03
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Li (huangli-itp) said : 		#3

Hi,

I checked the param_card.dat and find that , in madgraph sm ufo some parameters are different than the parameters in the FeynRules (why ? ). I use FeynRules to get a SM ufo then no problem.

Best,
Li

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

Hi,

We have some conceptual disagreement between FR and MG on what should be some value for some parameter.
For example, having the light quark mass different of zero is a non sense for MC point of view (most of the time)
but this is something important for FR author.
This is one of the reason why the FR default for the SM is NOT the model that is used by MG.

Cheers,

Olivier

> On Nov 10, 2015, at 10:37, Li <email address hidden> wrote:
>
> Question #273990 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/273990
>
> Li posted a new comment:
> Hi,
>
> I checked the param_card.dat and find that , in madgraph sm ufo some
> parameters are different than the parameters in the FeynRules (why ? ).
> I use FeynRules to get a SM ufo then no problem.
>
> Best,
> Li
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Li (huangli-itp) said : 		#5

Thanks Olivier Mattelaer, that solved my question.

Revision history for this message
Li (huangli-itp) said : 		#6

Hi, Olivier
  Thanks a lot !

Best,
Li