Forcing pyhtia8 decays

Since we are not able to do the gluon fusion at NLO (since we do not have the two loop computation available for such computation).
I'm not sure what you are doing and which part of our code you are using (are you using the infinite top mass limit?).

But I would suggest to use madspin in spinmode=none to do the decay since that mode is working at LO and at NLO.

Cheers,

Olivier

Dear Oliver,

Thank you very much for your reply!

 My statement was not precise. I a generating p p > H at NLO in the SM, hence I have gluon-fusion at one-loop (and no born diagram).
I am using this model http://feynrules.irmp.ucl.ac.be/wiki/HEFT_DH.

I am not familiar with madspin. Can I manually change the branching ratios of the decay particle?

Thank you very much again!

Best,
Guglielmo

Sorry, this still confuse me, are you using the HEFT_DH model or the SM model for your computation?

In the SM, g g > h, is part of the NNLO computation of "p p > h", even if I like to consider it as the LO contribution of "g g > h".
In both case this is proportional to as^2 and for the code point of view this is a LO computation (so you have access to the LO cuts, scale choice, options,...).

In the HEFT_DH, the "g g > h" is a tree level vertex and therefore the LO contribution in that model.
Obviously that model is only valid in the infinite top mass limit.

In that model you can either ask for g g > h at LO or doing p p > h at NLO accuracy.
I would consider it weird that you compute the loop-induced g g > h with that model since this is clearly not the point of such model.
I would guess that it can work, but I would advise to carefully check everything to be sure that you do not have double counting/...

> I am not familiar with madspin. Can I manually change the branching ratios of the decay particle?

In that mode, the BR is computed by the partial width divided by the total width, so if you provide a fake total width, you would have full control on the BR. Now at this stage, it is easy enough to just change the normalization of the sample that you provide.

Cheers,

Olivier

this is part of the LO computation

Dear Oliver,

Thank you very much for the detailed information. I am actually generating p p > h at NLO accuracy (integrating out the top). Thank you again for the explanation.

I am using madspin with the following card:

#************************************************************
#* MadSpin *
#* *
#* P. Artoisenet, R. Frederix, R. Rietkerk, O. Mattelaer *
#* *
#* Part of the MadGraph5_aMC@NLO Framework: *
#* The MadGraph5_aMC@NLO Development Team - Find us at *
#* https://server06.fynu.ucl.ac.be/projects/madgraph *
#* *
#* Manual: *
#* cp3.irmp.ucl.ac.be/projects/madgraph/wiki/MadSpin *
#* *
#************************************************************
#Some options (uncomment to apply)
#
# set seed 1
# set Nevents_for_max_weight 75 # number of events for the estimate of the max. weight
# set BW_cut 15 # cut on how far the particle can be off-shell
 set spinmode none # Use one of the madspin special mode
 set max_weight_ps_point 400 # number of PS to estimate the maximum for each event

# specify the decay for the final state particles
decay h > all all
# running the actual code
launch

and the following param card:

######################################################################
## PARAM_CARD AUTOMATICALY GENERATED BY MG5 FOLLOWING UFO MODEL ####
######################################################################
## ##
## Width set on Auto will be computed following the information ##
## present in the decay.py files of the model. ##
## See arXiv:1402.1178 for more details. ##
## ##
######################################################################

###################################
## INFORMATION FOR MASS
###################################
Block mass
    6 1.733000e+02 # MT
   15 1.777000e+00 # MTA
   23 9.118760e+01 # MZ
   24 8.041900e+01 # MW
   25 95 # MH
## Dependent parameters, given by model restrictions.
## Those values should be edited following the
## analytical expression. MG5 ignores those values
## but they are important for interfacing the output of MG5
## to external program such as Pythia.
  1 0.000000e+00 # d : 0.0
  2 0.000000e+00 # u : 0.0
  3 0.000000e+00 # s : 0.0
  4 0.000000e+00 # c : 0.0
  5 0.000000e+00 # b : 0.0
  11 0.000000e+00 # e- : 0.0
  12 0.000000e+00 # ve : 0.0
  13 0.000000e+00 # mu- : 0.0
  14 0.000000e+00 # vm : 0.0
  16 0.000000e+00 # vt : 0.0
  21 0.000000e+00 # g : 0.0
  22 0.000000e+00 # a : 0.0
  90002 9.118760e+01 # ghz : MZ
  90003 8.041900e+01 # ghwp : MW
  90004 8.041900e+01 # ghwm : MW
  250 9.118760e+01 # g0 : MZ
  251 8.041900e+01 # gp : MW

###################################
## INFORMATION FOR SMINPUTS
###################################
Block sminputs
    1 1.279000e+02 # aEWM1
    3 1.184000e-01 # aS (Note that Parameter not used if you use a PDF set)

###################################
## INFORMATION FOR DECAY
###################################
DECAY 6 1.508336e+00 # WT
DECAY 23 2.495200e+00 # WZ
DECAY 24 2.085000e+00 # WW
DECAY 25 1
# BR NDA ID1 ID2 ...
   1 2 22 22 # 2

## Dependent parameters, given by model restrictions.
## Those values should be edited following the
## analytical expression. MG5 ignores those values
## but they are important for interfacing the output of MG5
## to external program such as Pythia.
DECAY 1 0.000000e+00 # d : 0.0
DECAY 2 0.000000e+00 # u : 0.0
DECAY 3 0.000000e+00 # s : 0.0
DECAY 4 0.000000e+00 # c : 0.0
DECAY 5 0.000000e+00 # b : 0.0
DECAY 11 0.000000e+00 # e- : 0.0
DECAY 12 0.000000e+00 # ve : 0.0
DECAY 13 0.000000e+00 # mu- : 0.0
DECAY 14 0.000000e+00 # vm : 0.0
DECAY 15 0.000000e+00 # ta- : 0.0
DECAY 16 0.000000e+00 # vt : 0.0
DECAY 21 0.000000e+00 # g : 0.0
DECAY 22 0.000000e+00 # a : 0.0
DECAY 250 0.000000e+00 # g0 : 0.0
DECAY 251 0.000000e+00 # gp : 0.0
#===========================================================
# QUANTUM NUMBERS OF NEW STATE(S) (NON SM PDG CODE)
#===========================================================

Block QNUMBERS 90001 # gha
        1 0 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 90002 # ghz
        1 0 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 90003 # ghwp
        1 3 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 90004 # ghwm
        1 -3 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 90005 # ghg
        1 0 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 8 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 250 # g0
        1 0 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 0 # Particle/Antiparticle distinction (0=own anti)
Block QNUMBERS 251 # gp
        1 3 # 3 times electric charge
        2 1 # number of spin states (2S+1)
        3 1 # colour rep (1: singlet, 3: triplet, 8: octet)
        4 1 # Particle/Antiparticle distinction (0=own anti)

Then I am feeding to pythia8 and running Delphes. However, I am still not having a large number of photons as final states in the root file.

Thank you very much again!

Best,
Guglielmo Coloretti

You should ask MadSpin to decay only into photon...
You ask him to decay into "all all" so it will also do decay into gluon/b /...

Cheers,

Olivier

Dear Oliver,

I tried before decaying only to photons. But it gives me error.

Command "launch " interrupted with error:
NoDiagramException : No amplitudes generated from process Process: h > a a. Please enter a valid process
Please report this bug on https://bugs.launchpad.net/mg5amcnlo
More information is found in '/home/gcolor/Desktop/Softwares/MG5_aMC_v3_4_1/scratch/run_03_tag_1_debug.log'.
Please attach this file to your report.

If I am writing an effective model at LO where I include the higgs-photon-photon vertex, I think I could use this model in madspin (although it is not the model with which I generated the production process in madgraph).

Best,
Guglielmo Coloretti

Then it means that your model does not include h a a interactions.
you can change model for the madspin decay and use the heft model for that.
(be sure that all mass are the same for the param_card of the two models)

Cheers,

Olivier

Dear Oliver,

It worked! Thank you very much. I will read more about MadSpin and carefully. For the moment, I am running it as default (apart from changing the model and the param_card). I guess it should be fine.

Thank you very much again!

Best,
Guglielmo