di-higgs production for background

Hi,

The following should work:

import model loop_sm
generate g g > h h QED<=2 [noborn=QCD]
output
launch
madspin=none
decay h > b b~

As mention in the loop induced paper: arXiv:1507.00020
Madspin is not compatible with loop-induced mode.
For Higgs decay, you can either use the parton-shower or use the spinmode=none mode of madspin (introduced for that specific case)
Since the Higgs is scalar (so no spin correlation) and has a small width (so no sizeable offshell effect), it is actually a perfect method for the Higgs decay. (and using the normal/full maspin will actually jsut be a waste of cpu time)

Cheers,

Olivier

> On 21 Feb 2022, at 15:45, Shubhani Jain <email address hidden> wrote:
>
> New question #700694 on MadGraph5_aMC@NLO:
> https://answers.launchpad.net/mg5amcnlo/+question/700694
>
> Hi
>
> I want to generate some background events for process p p > hh >b b~ b b~ (where h is just standard model Higgs). I have tried using :
>
> 1) generate p p > h h , ( h > b b~ ),( h > b b~)
> 2) generate g g > h h [QCD] , then would have decayed h > b b~ in madpsin card
>
>
> But both options doesn't work. Is there a particular way to do this in MG5_aMC_v3_3_1 version of madgraph?
>
> Regards
> Shubhani
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Hi Olivier

Thanks for the explanation.

Yes, I do set madspin mode to none, that card is used just to decay h >b b~.

Regards
Shubhani

Hi

Sorry to open this question again. I want to generate pp >hh >bb~ bb~ at LO level but using generate g g > h h QED<=2 [noborn=QCD] :

 You are installing 'ninja', please cite ref(s): arXiv:1203.0291, arXiv:1403.1229, arXiv:1604.01363.
Downloading the HEPToolInstaller at:
   /mainfs/scratch/sj1n19/MG5/MG5_aMC_v3_3_1/vendor/OfflineHEPToolsInstaller.tar.gz
Now installing ninja. Be patient...
Detected 'ninja' missing dependency: 'oneloop'. Will install it now.
Installing tool 'oneloop'...
    > Follow the installation progress by running the command below in a separate terminal)
    > tail -f /mainfs/scratch/sj1n19/MG5/MG5_aMC_v3_3_1/HEPTools/oneloop/oneloop_install.log
    > Successful installation of dependency 'oneloop' in '/mainfs/scratch/sj1n19/MG5/MG5_aMC_v3_3_1/HEPTools'.
    > See installation log at '/mainfs/scratch/sj1n19/MG5/MG5_aMC_v3_3_1/HEPTools/oneloop/oneloop_install.log'.
Installing tool 'ninja'...
    > Follow the installation progress by running the command below in a separate terminal)
    > tail -f /mainfs/scratch/sj1n19/MG5/MG5_aMC_v3_3_1/HEPTools/ninja/ninja_install.log
A problem occured during the installation of 'ninja'.
Content of the installation log file '/mainfs/scratch/sj1n19/MG5/MG5_aMC_v3_3_1/HEPTools/ninja/ninja_install.log':

It shows that there are loop diagrams involved and started downloading ninja. Is there some other way of doing this?

Regards
Shubhani

Hi,

ninja is optional for your process, the best method to compute loop is likely collier (which is also optional).
We do have two mandatory code for loop computation: Cuttools and iregi. All the other code doing loop computation are optional.
(even if we strongly recommend ninja and collier)

Cheers,

Olivier

Hi Olivier

Actually, I want to generate these at LO level, I tried to just do p p > h h , ( h > b b~ ) , ( h > b b ~ ) using v2_7_2 and it works fine. I want to do the same with v3_3_1 which gives me an error if I do this. Using the couplings you have mentioned gives me loop diagrams which I am not interested in. Is there a way to replicate this in the latest version?

Regards
Shubhani

Hi,

What you did in 2.7.2 should still work in 3.3.1

Now
import model sm
generate p p > h h
should not work in the sm model.
The point is that "p" contains only massless quark that does not couple to the Higgs (physically they do but this is so small...)
and the gluon does not couple to the Higgs at tree-level.

Now they are way to make it work within 2.7.2 (with various approximation that are not really valid for your process) and those methods should still work in 3.3.1 (with the exact same physics limitation).

Now without knowing what approximation you found acceptable within 2.7.2, I can not comment more.
If you provide me the full script that you use in 2.7.2, I can double check that you can indeed do the same in 3.3.1 (or fix the issue if I face one).

Cheers,

Olivier

Hi Olivier

Using loop_sm and then generate p p > h h [QCD] using v2_7_2:
MG5_aMC>generate p p > h h [QCD]
The current model sm does not allow to generate loop corrections of type ['QCD'].
MG5_aMC now loads 'loop_sm'.
 import model loop_sm
INFO: Restrict model loop_sm with file models/loop_sm/restrict_default.dat .
INFO: Run "set stdout_level DEBUG" before import for more information.
INFO: Change particles name to pass to MG5 convention
Kept definitions of multiparticles l- / j / vl / l+ / p / vl~ unchanged
Defined multiparticle all = g gh gh~ d u s c d~ u~ s~ c~ a ve vm vt e- mu- ve~ vm~ vt~ e+ mu+ b t b~ t~ z w+ h w- ta- ta+
------------------------------------------------------------------------
 No Born diagrams found. Now switching to the loop-induced mode.
 Please cite ref. 'arXiv:1507.00020' when using results from this mode.
------------------------------------------------------------------------
WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
Make sure you did not want to include them.
WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
Make sure you did not want to include them.
WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
Make sure you did not want to include them.
WARNING: Some loop diagrams contributing to this process are discarded because they are not pure (QCD)-perturbation.
Make sure you did not want to include them.
1 processes with 16 diagrams generated in 2.737 s
Total: 1 processes with 16 diagrams
MG5_aMC>output check
INFO: initialize a new directory: check
INFO: remove old information in check
INFO: Organizing processes into subprocess groups
INFO: Generating Helas calls for process: g g > h h WEIGHTED<=8 [ noborn = QCD ]
INFO: Processing color information for loop process: g g > h h [ noborn = QCD ]
INFO: Creating color matrix loop process: g g > h h WEIGHTED<=8 [ noborn = QCD ]
INFO: Creating files in directory /scratch/sj1n19/MG5/MG5_aMC_v2_7_2/check/SubProcesses/PV0_0_1_gg_hh
ALOHA: aloha creates FFV1 set of routines with options: L1
INFO: Computing diagram color coefficients
INFO: Drawing loop Feynman diagrams for Process: g g > h h WEIGHTED<=8 [ noborn = QCD ]
INFO: Creating files in directory P0_gg_hh
INFO: Generating Feynman diagrams for Process: g g > h h WEIGHTED<=8 [ noborn = QCD ]
INFO: Finding symmetric diagrams for subprocess group gg_hh
Generated helas calls for 1 subprocesses (16 diagrams) in 0.207 s
ALOHA: aloha creates FFS1 set of routines with options: L2
ALOHA: aloha creates VVS1 routines
ALOHA: aloha creates SSS1 routines
ALOHA: aloha creates R2_GGHH routines
save configuration file to /scratch/sj1n19/MG5/MG5_aMC_v2_7_2/check/Cards/me5_configuration.txt
INFO: Use Fortran compiler gfortran
INFO: Use c++ compiler g++
INFO: Generate jpeg diagrams
INFO: Generate web pages
Output to directory /scratch/sj1n19/MG5/MG5_aMC_v2_7_2/check done.
Type "launch" to generate events from this process, or see
/scratch/sj1n19/MG5/MG5_aMC_v2_7_2/check/README
Run "open index.html" to see more information about this process.

Using v3_3_1:

MG5_aMC>import model loop_sm
INFO: Restrict model loop_sm with file models/loop_sm/restrict_default.dat .
INFO: Run "set stdout_level DEBUG" before import for more information.
INFO: Change particles name to pass to MG5 convention
Kept definitions of multiparticles p / j / l+ / l- / vl / vl~ unchanged
Defined multiparticle all = g gh gh~ d u s c d~ u~ s~ c~ a ve vm vt e- mu- ve~ vm~ vt~ e+ mu+ b t b~ t~ z w+ h w- ta- ta+
MG5_aMC>generate p p > h h [QCD]
INFO: Checking for minimal orders which gives processes.
INFO: Please specify coupling orders to bypass this step.
INFO: Trying coupling order WEIGHTED<=4: WEIGTHED IS QCD+2*QED
INFO: Trying coupling order WEIGHTED<=5: WEIGTHED IS QCD+2*QED
INFO: Trying coupling order WEIGHTED<=6: WEIGTHED IS QCD+2*QED
INFO: Trying coupling order WEIGHTED<=7: WEIGTHED IS QCD+2*QED
Error detected in "generate p p > h h [QCD]"
write debug file MG5_debug
If you need help with this issue please contact us on https://answers.launchpad.net/mg5amcnlo
str :
 Automatic process-order determination lead to negative constraints:
 QED: 6, QCD: -4
 Please specify the coupling orders from the command line.

This is the difference I am facing in v3_3_1, same with just g g > h h [QCD].

Regards
Shubhani

But this is a loop-induced process. If you look at the log this is clearly written:

------------------------------------------------------------------------
 No Born diagrams found. Now switching to the loop-induced mode.
 Please cite ref. 'arXiv:1507.00020' when using results from this mode.
------------------------------------------------------------------------

So that computation is the one you can do in 3.3.1 as

import model loop_sm
generate g g > h h QED<=2 [noborn=QCD]
output
launch
madspin=none
decay h > b b~

So I do not understand your objection about loop-induced process?

Cheers,

Olivier

Hi Olivier

Thanks for the help.

I will follow the steps and will check the .lhe file whether I am getting the particles I would want to hadronize later.

Regards
Shubhani