Bottom associated Higgs production

Hi,

I will refer you to this paper: arXiv:1409.5301
Which study exactly the difference between the two schemes.

For the technical details. it depends of the model.
Indeed the definition of the proton and jet automatically include the b-quark if that one is massless in the model.

So assuming the you do that in the standard model (our SM is 4 flavor)
you can either do (4 flavor)
import model sm
generate p p > j j h

or you can do (5 flavor)
import model sm-no_b_mass
generate p p > h

Cheers,

Olivier

PS: this behavior is different in old version of the code.

> On Jan 23, 2016, at 13:17, Jan Hajer <email address hidden> wrote:
>
> New question #283103 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/283103
>
> Hi,
>
> I want to calculate the crosssection and kinematics of bottom associated (heavy) Higgs production.
> I am planning to apply b-tags on both bottom jets.
> Which process gives me the best kinematics and crosssection, is it g g -> b b~ h2 in 4 flavor scheme or b b~ > h2 in 5 flavor scheme?
> Also I have trouble to figure out the precise steps I have to take in order to switch between these two schemes, besides changing the process.
>
> Best,
> Jan
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi,

Thank you for the reference. It seems that the model files
  loop_sm_MSbar_yb
  loop_sm_MSbar_yb-no_b_mass
are crucial to reproduces their results. Do you know it these model files are public and will work with version 2.3.3?

Furthermore, the model: model sm-no_b_mass does not allow for the process p p > h. It leads to:

Command "generate p p > h" interrupted with error:
NoDiagramException : No amplitudes generated from process Process: g/u/c/d/s/u~/c~/d~/s~/b/b~ g/u/c/d/s/u~/c~/d~/s~/b/b~ > h WEIGHTED=2 @1. Please enter a valid process

Best,
Jan

Dear Hajer,

> Do you know it these model files are public and will work with version 2.3.3?

Public I do not know at least it is not available on feynrules website.
Please contact one of the author of the paper by email to ask them.
It should be working in 2.3.3

Note that if you do not want to do NLO/loop-induced, you do not need that model and the default sm, will be ok.

> Furthermore, the model: model sm-no_b_mass does not allow for the
> process p p > h. It leads to:
>
> Command "generate p p > h" interrupted with error:
> NoDiagramException : No amplitudes generated from process Process: g/u/c/d/s/u~/c~/d~/s~/b/b~ g/u/c/d/s/u~/c~/d~/s~/b/b~ > h WEIGHTED=2 @1. Please enter a valid process

This is normal since this is not a tree-level diagram.
If you want to have the loop-induced diagram you can do
generate p p > h [QCD]
if you want to use the Effective vertex approach then you can use the heft model
import model heft-no_b_mass
generate p p > h

Cheers,

Olivier

> On Jan 24, 2016, at 08:38, Jan Hajer <email address hidden> wrote:
>
> Question #283103 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/283103
>
> Status: Answered => Open
>
> Jan Hajer is still having a problem:
> Hi,
>
> Thank you for the reference. It seems that the model files
> loop_sm_MSbar_yb
> loop_sm_MSbar_yb-no_b_mass
> are crucial to reproduces their results. Do you know it these model files are public and will work with version 2.3.3?
>
> Furthermore, the model: model sm-no_b_mass does not allow for the
> process p p > h. It leads to:
>
> Command "generate p p > h" interrupted with error:
> NoDiagramException : No amplitudes generated from process Process: g/u/c/d/s/u~/c~/d~/s~/b/b~ g/u/c/d/s/u~/c~/d~/s~/b/b~ > h WEIGHTED=2 @1. Please enter a valid process
>
> Best,
> Jan
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier,

I already got an answer, the code for the 4FS can be found on
https://cp3.irmp.ucl.ac.be/projects/madgraph/wiki/bbH#no1

I am still confused about the 5FS process with the sm model file.
Of course I can switch on loop induced couplings for the 4FS when I do

import model sm
generate g g > h [QCD]

but when I load the no-b-mass restriction file, i don't get a result for

import model sm-no_b_mass
generate b b~ > h [QCD]

on the other hand when I keep the bottom mass I can do

import model sm
generate b b~ > h

and do get a diagram. I but in this case I am not really in the 5FS.
Hence my question how to switch properly to the 5FS for this process.

Thanks for you r help,
Jan

Dear Jan,

Since the mass of the b is zero the bb~h couplings is zero as well and therefore explains why the bb~h couplings do not exists.
Keeping the yukawa different of zero is possible but then you have problem if you perform computation in Feynman gauge (which is not default but ok).

If you want to keep the yukawa mass but set the pole mass to zero, the cleanest way is to
1) copy the file (from models/sm)
restrict_no_b_mass.dat
to
restrict_5fs.dat
and put back the yukawa mass different of zero.

Cheers,

Olivier

Thanks