MadGraph5_aMC@NLO

Higgs branching ratio and the MSSM

Asked by Adarsh Pyarelal

Hello,

I'm having trouble with understanding the cross-sections that I obtain from MG5.

For the first process, here is the generation syntax:

***
import model mssm-full
generate p p > n2 n3, (n2 > z n1), (n3 > h1 n1)
add process p p > n2 n3, (n3 > z n1), (n2 > h1 n1)
***

I used SUSY-HIT to calculate a particle spectrum and decay widths, and used those values for my param_card.dat

The decay width for the higgs is 3.9 MeV, which is in the same ballpark as the 4.07 MeV from http://pdg.lbl.gov/2013/reviews/rpp2013-rev-higgs-boson.pdf. The branching ratio for h1 (the SM higgs) -> bb is 0.63 for a SM higgs mass of 124, which is close to what we see here: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/CERNYellowReportPageBR2014

The cross-section I get is 7.8 fb.

However, when I decay the higgs explicitly:

***
generate p p > n2 n3, (n2 > z n1), (n3 > h1 n1, h1 > b b~)
add process p p > n2 n3, (n3 > z n1), (n2 > h1 n1, h1 > b b~)
***

I get a cross-section of 2.6 fb, when I would have expected 0.63*7.8 = 4.9 fb.

Both have the following parameters
cut_decays = False
bwcutoff = 15
I've also removed all the pt and eta cuts from the run_card.dat.

Reducing the decay width of the higgs manually in the param_card.dat helps increase the cross-section, but to get it to 4.9 fb, I would have to put the higgs decay width to about 2 MeV, which is about half the actual value.

If I change the branching ratio of h->bb in the param_card.dat, nothing changes either.

Do you know why this might be? I don't have the same trouble when studying the branching ratio of Z->l+ l- ... I recover the expected cross section when I set cut_decays = False and reduce bwcutoff to 10.

-Adarsh

Question information

Language:
English Edit question
Status:
Solved
For:
MadGraph5_aMC@NLO Edit question
Assignee:
No assignee Edit question
Solved by:
Olivier Mattelaer
Solved:
Last query:
Last reply:
Revision history for this message
Adarsh Pyarelal (adarsh-pyarelal) said : 		#1

My param_card.dat:

#
# ======================
# | THE SUSYHIT OUTPUT |
# ======================
#
#
# ------------------------------------------------------
# | This is the output of the SUSY-HIT package |
# | created by A.Djouadi, M.Muehlleitner and M.Spira. |
# | In case of problems with SUSY-HIT email to |
# | <email address hidden> |
# | <email address hidden> |
# | <email address hidden> |
# ------------------------------------------------------
#
# ------------------------------------------------------
# | SUSY Les Houches Accord - MSSM Spectrum + Decays |
# | based on the decay programs |
# | |
# | SDECAY 1.5 |
# | |
# | Authors: M.Muhlleitner, A.Djouadi and Y.Mambrini |
# | Ref.: Comput.Phys.Commun.168(2005)46 |
# | [hep-ph/0311167] |
# | |
# | HDECAY 3.4 |
# | |
# | By: A.Djouadi,J.Kalinowski,M.Muhlleitner,M.Spira |
# | Ref.: Comput.Phys.Commun.108(1998)56 |
# | [hep-ph/9704448] |
# | |
# | |
# | If not stated otherwise all DRbar couplings and |
# | soft SUSY breaking masses are given at the scale |
# | Q= 0.80009795E+04
# | |
# ------------------------------------------------------
#
#
BLOCK DCINFO # Decay Program information
     1 SDECAY/HDECAY # decay calculator
     2 1.5 /3.4 # version number
#
BLOCK SPINFO # Spectrum calculator information
     1 SuSpect # RGE +Spectrum calculator
     2 2.41 # version number
#
BLOCK MODSEL # Model selection
     1 0 # #general MSSM low scale
#
BLOCK SMINPUTS # Standard Model inputs
         1 1.27934000E+02 # alpha_em^-1(M_Z)^MSbar
         2 1.16639000E-05 # G_F [GeV^-2]
         3 1.17200000E-01 # alpha_S(M_Z)^MSbar
         4 9.11870000E+01 # M_Z pole mass
         5 4.25000000E+00 # mb(mb)^MSbar
         6 1.72500000E+02 # mt pole mass
         7 1.77710000E+00 # mtau pole mass
#
BLOCK MINPAR # Input parameters - minimal models
         1 0.00000000E+00 #

Revision history for this message
Adarsh Pyarelal (adarsh-pyarelal) said : 		#2

Relevant decays:
# PDG Width
DECAY 1000022 0.00000000E+00 # neutralino1 decays
#
# PDG Width
DECAY 1000023 6.71713897E-01 # neutralino2 decays
# BR NDA ID1 ID2
     3.00976306E-01 2 1000022 23 # BR(~chi_20 -> ~chi_10 Z )
     6.99023694E-01 2 1000022 25 # BR(~chi_20 -> ~chi_10 h )
#
# PDG Width
DECAY 1000025 6.65036555E-01 # neutralino3 decays
# BR NDA ID1 ID2
     6.90117051E-01 2 1000022 23 # BR(~chi_30 -> ~chi_10 Z )
     3.09882949E-01 2 1000022 25 # BR(~chi_30 -> ~chi_10 h )
#
# PDG Width
DECAY 1000035 2.49681054E+01 # neutralino4 decays
# BR NDA ID1 ID2
     3.03468512E-05 2 1000022 23 # BR(~chi_40 -> ~chi_10 Z )
     3.54657489E-02 2 1000023 23 # BR(~chi_40 -> ~chi_20 Z )
     2.16274060E-01 2 1000025 23 # BR(~chi_40 -> ~chi_30 Z )
     2.42179882E-01 2 1000024 -24 # BR(~chi_40 -> ~chi_1+ W-)
     2.42179882E-01 2 -1000024 24 # BR(~chi_40 -> ~chi_1- W+)
     3.96627827E-06 2 1000022 25 # BR(~chi_40 -> ~chi_10 h )
     2.26870027E-01 2 1000023 25 # BR(~chi_40 -> ~chi_20 h )
     3.69960864E-02 2 1000025 25 # BR(~chi_40 -> ~chi_30 h )
#
# PDG Width
DECAY 25 3.97819923E-03 # h decays
# BR NDA ID1 ID2
     6.32227375E-01 2 5 -5 # BR(h -> b bb )
     6.45984523E-02 2 -15 15 # BR(h -> tau+ tau- )
     2.28633302E-04 2 -13 13 # BR(h -> mu+ mu- )
     4.85273144E-04 2 3 -3 # BR(h -> s sb )
     2.11178735E-02 2 4 -4 # BR(h -> c cb )
     6.74587153E-02 2 21 21 # BR(h -> g g )
     2.29011197E-03 2 22 22 # BR(h -> gam gam )
     1.44580464E-03 2 22 23 # BR(h -> Z gam )
     1.86827521E-01 2 24 -24 # BR(h -> W+ W- )
     2.33202404E-02 2 23 23 # BR(h -> Z Z )

Revision history for this message
Adarsh Pyarelal (adarsh-pyarelal) said : 		#3

Relevant masses:

BLOCK MASS # Mass Spectrum
# PDG code mass particle
        24 8.04975777E+01 # W+
        25 1.24045024E+02 # h
        35 8.00005089E+03 # H
        36 8.00000000E+03 # A
        37 8.00064993E+03 # H+
         5 4.87877839E+00 # b-quark pole mass calculated from mb(mb)_Msbar
   1000001 8.00020086E+03 # ~d_L
   2000001 8.00004056E+03 # ~d_R
   1000002 7.99983969E+03 # ~u_L
   2000002 7.99991888E+03 # ~u_R
   1000003 8.00020086E+03 # ~s_L
   2000003 8.00004056E+03 # ~s_R
   1000004 7.99983969E+03 # ~c_L
   2000004 7.99991888E+03 # ~c_R
   1000005 7.99877010E+03 # ~b_1
   2000005 8.00147175E+03 # ~b_2
   1000006 7.97891392E+03 # ~t_1
   2000006 8.02310600E+03 # ~t_2
   1000011 8.00011974E+03 # ~e_L
   2000011 8.00012168E+03 # ~e_R
   1000012 7.99975857E+03 # ~nu_eL
   1000013 8.00011974E+03 # ~mu_L
   2000013 8.00012168E+03 # ~mu_R
   1000014 7.99975857E+03 # ~nu_muL
   1000015 7.99908899E+03 # ~tau_1
   2000015 8.00115269E+03 # ~tau_2
   1000016 7.99975857E+03 # ~nu_tauL
   1000021 1.40000000E+04 # ~g
   1000022 9.93780486E+01 # ~chi_10
   1000023 9.99551931E+02 # ~chi_20
   1000025 -1.00129938E+03 # ~chi_30
   1000035 3.00236940E+03 # ~chi_40
   1000024 9.98797993E+02 # ~chi_1+
   1000037 3.00236953E+03 # ~chi_2+

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

Hi,

I do not know the precision of SUSYHIT, up to which precision do they compute the width?
If you set the width to Auto, what value did you get?
The total width is certainly wrong for the higgs (due to the missing loop-induced decay) but comparing both number can be usefull and comparing if both
partial width h1 > b b~ are equal would be very critical.

Cheers,

Olivier

> On Jun 10, 2016, at 01:47, Adarsh Pyarelal <email address hidden> wrote:
>
> Question #295115 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/295115
>
> Adarsh Pyarelal gave more information on the question:
> Relevant masses:
>
> BLOCK MASS # Mass Spectrum
> # PDG code mass particle
> 24 8.04975777E+01 # W+
> 25 1.24045024E+02 # h
> 35 8.00005089E+03 # H
> 36 8.00000000E+03 # A
> 37 8.00064993E+03 # H+
> 5 4.87877839E+00 # b-quark pole mass calculated from mb(mb)_Msbar
> 1000001 8.00020086E+03 # ~d_L
> 2000001 8.00004056E+03 # ~d_R
> 1000002 7.99983969E+03 # ~u_L
> 2000002 7.99991888E+03 # ~u_R
> 1000003 8.00020086E+03 # ~s_L
> 2000003 8.00004056E+03 # ~s_R
> 1000004 7.99983969E+03 # ~c_L
> 2000004 7.99991888E+03 # ~c_R
> 1000005 7.99877010E+03 # ~b_1
> 2000005 8.00147175E+03 # ~b_2
> 1000006 7.97891392E+03 # ~t_1
> 2000006 8.02310600E+03 # ~t_2
> 1000011 8.00011974E+03 # ~e_L
> 2000011 8.00012168E+03 # ~e_R
> 1000012 7.99975857E+03 # ~nu_eL
> 1000013 8.00011974E+03 # ~mu_L
> 2000013 8.00012168E+03 # ~mu_R
> 1000014 7.99975857E+03 # ~nu_muL
> 1000015 7.99908899E+03 # ~tau_1
> 2000015 8.00115269E+03 # ~tau_2
> 1000016 7.99975857E+03 # ~nu_tauL
> 1000021 1.40000000E+04 # ~g
> 1000022 9.93780486E+01 # ~chi_10
> 1000023 9.99551931E+02 # ~chi_20
> 1000025 -1.00129938E+03 # ~chi_30
> 1000035 3.00236940E+03 # ~chi_40
> 1000024 9.98797993E+02 # ~chi_1+
> 1000037 3.00236953E+03 # ~chi_2+
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Adarsh Pyarelal (adarsh-pyarelal) said : 		#5

1. I set SUSY-HIT to compute widths to the maximum precision possible:

Block SU_ALGO
    2 21 # 2-loop RGE
    3 1 # g_1(gut) = g_2(gut) is consistently calculated from input
    4 2 # RGE accuracy: accurate (but slightly slower)
    6 0 # mA_pole and \mu(EWSB) input
    7 1 # No radiative corrections in squarks and gauginos
    8 1 # EWSB scale=sqrt(mt_L*mt_R)
    9 2 # Final spectrum accuracy: 0.01%
    10 2 # one loop + Dominant DSVZ 2-loop r.c. to Higgs mass

2. When I set the width for the higgs decay to Auto, I get the following error:

Command "survey" interrupted in sub-command: "set max_npoint_for_channel 0" with error:
MadGraph5Error: Invalid restriction card (not same block)

set(['umix', 'ae', 'ad', 'msoft', 'au', 'decay', 'minpar', 'staumix', 'ye', 'yd', 'alpha', 'modsel', 'sminputs', 'yu', 'stopmix', 'nmix', 'sbotmix', 'extpar', 'vmix', 'mass', 'gauge', 'hmix']) != set(['umix', 'snumix', 'msoft', 'msu2', 'vckm', 'fralpha', 'upmns', 'msd2', 'msl2', 'decay', 'tu', 'selmix', 'td', 'te', 'usqmix', 'dsqmix', 'ye', 'yd', 'sminputs', 'yu', 'mse2', 'nmix', 'vmix', 'msq2', 'mass', 'hmix']).
    Missing block: te,snumix,msl2,msq2,dsqmix,tu,selmix,msu2,vckm,usqmix,td,fralpha,upmns,mse2,msd2
    Unknown block : sbotmix,ae,ad,minpar,extpar,au,alpha,modsel,staumix,stopmix,gauge

3. However, when I input the spectrum from Suspect2 into the MadEvent MSSM decay width calculator (http://madgraph.hep.uiuc.edu/Calculators/mssm/mssm_calc.html), I get the decay width of the higgs as 1.93 MeV, which is considerably less than 4.07 MeV measured at the LHC and 3.9 predicted by SUSY-HIT, but gives us the right value to reproduce the expected branching ratio. Do you know why this might be?

Revision history for this message
Best Olivier Mattelaer (olivier-mattelaer) said : 		#6

Hi,

The I guess this is due to a mismatch between the LO width and the NLO width.
To reproduce the BR, you have to be consistent with the order of the computation that you perform (i.e. use the LO width)
Using a NLO width will on the other hand highly change your cross-section in your case.

Cheers,

Olivier

> On Jun 11, 2016, at 19:46, Adarsh Pyarelal <email address hidden> wrote:
>
> Question #295115 on MadGraph5_aMC@NLO changed:
> https://answers.launchpad.net/mg5amcnlo/+question/295115
>
> Status: Answered => Open
>
> Adarsh Pyarelal is still having a problem:
> 1. I set SUSY-HIT to compute widths to the maximum precision possible:
>
>
> Block SU_ALGO
> 2 21 # 2-loop RGE
> 3 1 # g_1(gut) = g_2(gut) is consistently calculated from input
> 4 2 # RGE accuracy: accurate (but slightly slower)
> 6 0 # mA_pole and \mu(EWSB) input
> 7 1 # No radiative corrections in squarks and gauginos
> 8 1 # EWSB scale=sqrt(mt_L*mt_R)
> 9 2 # Final spectrum accuracy: 0.01%
> 10 2 # one loop + Dominant DSVZ 2-loop r.c. to Higgs mass
>
>
> 2. When I set the width for the higgs decay to Auto, I get the following error:
>
> Command "survey" interrupted in sub-command: "set max_npoint_for_channel 0" with error:
> MadGraph5Error: Invalid restriction card (not same block)
>
> set(['umix', 'ae', 'ad', 'msoft', 'au', 'decay', 'minpar', 'staumix', 'ye', 'yd', 'alpha', 'modsel', 'sminputs', 'yu', 'stopmix', 'nmix', 'sbotmix', 'extpar', 'vmix', 'mass', 'gauge', 'hmix']) != set(['umix', 'snumix', 'msoft', 'msu2', 'vckm', 'fralpha', 'upmns', 'msd2', 'msl2', 'decay', 'tu', 'selmix', 'td', 'te', 'usqmix', 'dsqmix', 'ye', 'yd', 'sminputs', 'yu', 'mse2', 'nmix', 'vmix', 'msq2', 'mass', 'hmix']).
> Missing block: te,snumix,msl2,msq2,dsqmix,tu,selmix,msu2,vckm,usqmix,td,fralpha,upmns,mse2,msd2
> Unknown block : sbotmix,ae,ad,minpar,extpar,au,alpha,modsel,staumix,stopmix,gauge
>
> 3. However, when I input the spectrum from Suspect2 into the MadEvent
> MSSM decay width calculator
> (http://madgraph.hep.uiuc.edu/Calculators/mssm/mssm_calc.html), I get
> the decay width of the higgs as 1.93 MeV, which is considerably less
> than 4.07 MeV measured at the LHC and 3.9 predicted by SUSY-HIT, but
> gives us the right value to reproduce the expected branching ratio. Do
> you know why this might be?
>
> --
> You received this question notification because you are an answer
> contact for MadGraph5_aMC@NLO.

Revision history for this message
Adarsh Pyarelal (adarsh-pyarelal) said : 		#7

Okay, I compared the decay widths again - looks like the online calculator uses SDECAY to calculate the decay widths of the SUSY particles at LO. But SUSY-HIT uses HDECAY as well, and includes additional decay modes of the SM higgs. So I suppose it is more accurate.

Revision history for this message
Adarsh Pyarelal (adarsh-pyarelal) said : 		#8

Thanks Olivier Mattelaer, that solved my question.