Consequence of branching ratio larger than one in MadSpin
Dear MadGraph experts,
Hi. I am generating a loop-induced process and want to decay the final state using MadSpin, with spinmode none. I chose `none` spinmode since I am generating a scalar particle with a narrow width.
I want to decay a scalar resonance eta0 to two W bosons, and all of them decay hadronically.
Process: p p > iota0 > eta0 h
Higgs decay: h > b b~
eta0 decay: eta0 > w+ w- > q q q q
By specifying the width of eta0, I get a critical warning like `Branching ratio larger than one for 99925`.
If I choose to use Auto width for eta0, I don't get a warning. My guess is that it is related to eta0 > w+w- mode.
I will add my cards related to the above
proc_card.dat
set group_subprocesses Auto
set ignore_
set low_mem_
set complex_mass_scheme False
set include_
set gauge unitary
set loop_optimized_
set loop_color_flows False
set max_npoint_
set default_
set max_t_for_channel 99
set zerowidth_tchannel True
set nlo_mixed_expansion True
import model sm
define p = g u c d s u~ c~ d~ s~
define j = g u c d s u~ c~ d~ s~
define l+ = e+ mu+
define l- = e- mu-
define vl = ve vm vt
define vl~ = ve~ vm~ vt~
import model loop_sm_twoscalar
define p = g u c d s u~ c~ d~ s~
define j = g u c d s u~ c~ d~ s~
generate p p > iota0 > eta0 H QED<=4 [noborn=QCD]
output -f -nojpeg
Mass block and Decay block from param_card.dat
BLOCK MASS #
5 4.700000e+00 # mb
6 1.730000e+02 # mt
15 1.777000e+00 # mta
23 9.118800e+01 # mz
25 1.250000e+02 # mh
99925 1.000000e+03 # meta
99926 2.000000e+03 # miota
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
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
24 8.041900e+01 # w+ : cmath.sqrt(
DECAY 6 1.491500e+00 # wt
DECAY 23 2.441404e+00 # wz
DECAY 24 2.047600e+00 # ww
DECAY 25 6.382339e-03 # wh
DECAY 99925 1.000000e-02 #
DECAY 99926 1.000000e-02 #
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
Finally, MadSpin Card
# set Nevents_
# set BW_cut 15 # cut on how far the particle can be off-shell
set max_weight_ps_point 400 # number of PS to estimate the maximum for each event
#
set seed 474706
set spinmode none
define q = u c d s b u~ c~ d~ s~ b~
# specify the decay for the final state particles
decay eta0 > w+ w- > q q q q
decay h > b b~
# running the actual code
launch
By reading a few similar questions on this forum, I understand that this is due to the BR calculation for eta0 > WW decay. Numerator from LO calculation, denominator, which the specified width, being too small.
My questions are
1. What is the consequence, or possible bias in decays I can get with BR > 1 warning?
2. If there is, will it be relevant to my eta0 > w+ w- > qqqq decays? I am generating one kind of eta0 decays, no other modes are specified.
3. Is my approach of using 'set spinmode none' correct for the loop-induced process? If you have any recommendations for eta0 > w+ w- > qqqq decays, it will be great!
Thanks,
JaeJin
Question information
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- Solved by:
- Olivier Mattelaer
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