NLO computation with sm-c_mass

Asked by Mathieu

Dear MadGraph developers,

I am trying to produce Higgs using qqbar massive initial states (alone and in association with a jet).
I succeeded to do it at leading order.
By loading the sm-c_mass model or by putting the b quark in the proton and in the jet definition.

Now for the next-to-leading order in QCD, I do:

MG5_aMC>import model sm-c_mass

and

MG5_aMC>generate p p > h [QCD]
or
MG5_aMC>generate p p > h j [QCD]

I get the warning:

WARNING: Process: g/u/c/d/s/u~/c~/d~/s~ g/u/c/d/s/u~/c~/d~/s~ > h WEIGHTED=2 [ all = QCD ] can have real emission processes which are not finite.
To avoid this, please use multiparticles when generating the process and be sure to include all the following particles in the multiparticle definition:
 g, s, u, d, d~, u~, s~

and then when it is computing it, I get:

INFO: Setting up grid
INFO: Idle: 0, Running: 2, Completed: 0 [ current time: 10h47 ]
INFO: Idle: 0, Running: 0, Completed: 2 [ 3.9s ]
grep: P*/GF*/res_0: No such file or directory
Traceback (most recent call last):
  File "./sumres.py", line 131, in <module>
    (totABS, math.sqrt(errABS), math.sqrt(errABS)/totABS *100.,tot, math.sqrt(err), math.sqrt(err)/tot *100.)
ZeroDivisionError: float division by zero
INFO: Return code of the event collection: None
INFO: Output of the event collection:
N of directories: 2
Determining the number of unweighted events per channel
2 jobs did not terminate correctly:
P0_ccx_h/GF1
P0_cxc_h/GF1
The results are probably not correct. Please check the relevant log files corresponding to the above jobs for more information.
Found 0 correctly terminated jobs
0 2
Integrated abs(cross-section)
Integrated cross-section

If I try to define b in the proton, when I calculate the process at NLO, it automatically comes back to the definition without b in the PDF.
Thus, it computes the loop induced process and not the tree level one.

Computing p p > c c [QCD] did not work either.

Do you see how I could resolve this issue?

Cheers,

Mathieu

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
marco zaro Edit question
Solved by:
marco zaro
Solved:
Last query:
Last reply:
Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#1

Dear Matthieu,

If you you use massive b/c, it is important to not have those particle in the proton definition.

Cheers,

Olivier
On 18 Sep 2015, at 14:37, Mathieu <email address hidden> wrote:

> New question #271531 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/271531
>
> Dear MadGraph developers,
>
> I am trying to produce Higgs using qqbar massive initial states (alone and in association with a jet).
> I succeeded to do it at leading order.
> By loading the sm-c_mass model or by putting the b quark in the proton and in the jet definition.
>
> Now for the next-to-leading order in QCD, I do:
>
> MG5_aMC>import model sm-c_mass
>
> and
>
> MG5_aMC>generate p p > h [QCD]
> or
> MG5_aMC>generate p p > h j [QCD]
>
> I get the warning:
>
> WARNING: Process: g/u/c/d/s/u~/c~/d~/s~ g/u/c/d/s/u~/c~/d~/s~ > h WEIGHTED=2 [ all = QCD ] can have real emission processes which are not finite.
> To avoid this, please use multiparticles when generating the process and be sure to include all the following particles in the multiparticle definition:
> g, s, u, d, d~, u~, s~
>
> and then when it is computing it, I get:
>
> INFO: Setting up grid
> INFO: Idle: 0, Running: 2, Completed: 0 [ current time: 10h47 ]
> INFO: Idle: 0, Running: 0, Completed: 2 [ 3.9s ]
> grep: P*/GF*/res_0: No such file or directory
> Traceback (most recent call last):
> File "./sumres.py", line 131, in <module>
> (totABS, math.sqrt(errABS), math.sqrt(errABS)/totABS *100.,tot, math.sqrt(err), math.sqrt(err)/tot *100.)
> ZeroDivisionError: float division by zero
> INFO: Return code of the event collection: None
> INFO: Output of the event collection:
> N of directories: 2
> Determining the number of unweighted events per channel
> 2 jobs did not terminate correctly:
> P0_ccx_h/GF1
> P0_cxc_h/GF1
> The results are probably not correct. Please check the relevant log files corresponding to the above jobs for more information.
> Found 0 correctly terminated jobs
> 0 2
> Integrated abs(cross-section)
> Integrated cross-section
>
> If I try to define b in the proton, when I calculate the process at NLO, it automatically comes back to the definition without b in the PDF.
> Thus, it computes the loop induced process and not the tree level one.
>
> Computing p p > c c [QCD] did not work either.
>
> Do you see how I could resolve this issue?
>
> Cheers,
>
> Mathieu
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Mathieu (pellen) said :
#2

Dear Olivier,

I want to have the Higgs coupling to the c (possibly the b) in the proton.
I tried to use the sm-c_mass model at NLO, generate the process and then set the mass to zero in the param_card.dat.
But this did not work either.
Is there a way to have Higgs production from qqbar (i.e. without loop induced) initiated channel then?

Cheers,

Mathieu

Revision history for this message
Olivier Mattelaer (olivier-mattelaer) said :
#3

Dear Matthieu,

@LO this is possible.
@NLO this is technically possible but you need to create via FeynRules a dedicated UFO model where you change the renormalisation scheme in order to keep separate (in a consistent way) the pole mass and the coupling to the Higgs.
Such type of model exists for the Charged Higss case but I never heard of the equivalent for the SM.
I assign Marco to this since he is one of the author of the Charged Higgs paper.

Cheers,

Olivier

Revision history for this message
Best marco zaro (marco-zaro) said :
#4

Dear Mathieu,
I would suggest you to create a restriction analogous to the c-mass where you put the charm kinematic mass to 0 butyou keep !=0 the charm yukawa. this way c c > h will work consinstently.
Also, you can have a look at this paper
Wieseman et al, arXiv:1409.5301
where the bb>h process is computed both in the 4 and 5 flavour scheme, and possibly contact Marius Wiesemann for further questions. In particular for what concerns the renormalisation of the Yukawa in the msbar scheme, which is useful as it resums logs of m_b/mh (mc/mh in your case)

Let me know if you manage to work out the first part of my answer, that should not be complicated...

Cheers,

Marco

Revision history for this message
Mathieu (pellen) said :
#5

Thanks marco zaro, that solved my question.