DM pair production in 2HDM extended by a complex scalar singlet

Hi Tabira,
the signature that you are describing (ee -> XXgamma) is the typical for a WIMP like e.g. the neutralino which is either produced via s-channel Z exchange or t-channel selectron exchange. In this case you need a photon for detection. For Higgs-portal like models where the Higgs is the mediator (or decays into two DM particles) the production process at a Higgs factory would be ee -> ZH (signature: invisible Higgs decay) or ee -> vvH. The latter then indeed produces only invisible particles (I needed to write the answer to understand that myself). Indeed, in this case the process you should sample is either fully off-shell ee -> vvXXgamma (2->5) or
ee->vvHgamma (2->4) and the subsequent decay H->XX with the unstable option. The error shown above results from the fact that you got a zero cross section. This can happen if the process does not exist (e.g. e+ e- -> W+ Z would give you vanishing cross section; this doesn't choke in case you have a typo in long lists of processes), or the process exists according to the Feynman rules but the coupling constants are zero. Please check the used (UFO) model for details.
Cheers,
    Juergen

I have deleted my previous comment. the couplings on the ufo are indeed set to zero. I shall get back to you once it gets fixed.

So just an update. I reset the coupling values, and just to check the ufo was fine, I ran the process ee > hvv and it gave me ~47fb for h = 125 GeV which is what one would expect. so then I ran the process ee>vvXXgamma and it gave me a cross section as low as 3.2470017E-18 +- 1.57E-19 fb, and I am quite baffled by it. Not sure why this is happening.

Tabira, it is always best to reduce the test case as much as possible, so when evaluating don't use ISR etc., just a bare integration. That was at 350 GeV, I assume? The additional photon will give you roughly a factor 1/137 suppression compared to the process ee -> vvXX, so could you please test the latter first? Then, if you just have a photon in the final state and there are no cuts, the result will not be finite or converge. Whizard per default does not apply cuts. I would guess that your integration was just producing numerical noise and not a reliable result. You need an lower energy cut on the photon and an angular separation from the beam axis.

Hi,

I tried to just run the process ee>vvXX and I was still getting something 10^-18 scale. we thought maybe it was due to the lower branching to XX so we looked for another set of benchmark points that would give us a higher branching and decided to test it out again, but the output doesn't look right.

 Phase space: 23 channels, 8 dimensions
| Phase space: found 23 channels, collected in 9 groves.
| Phase space: Using 58 equivalences between channels.
| Phase space: wood
Warning: No cuts have been defined.
| Starting integration for process 'eehvv'
| Integrate: iterations not specified, using default
| Integrate: iterations = 10:10000:"gw", 5:20000:""
| Integrator: 9 chains, 23 channels, 8 dimensions
| Integrator: Using VAMP channel equivalences
| Integrator: 10000 initial calls, 20 bins, stratified = T
| Integrator: VAMP
|=============================================================================|
| It Calls Integral[fb] Error[fb] Err[%] Acc Eff[%] Chi2 N[It] |
|=============================================================================|
| VAMP: parameter mismatch, discarding grid file 'eehvv.m1.vg'
   1 9982 2.0413396E+00 1.94E+00 94.86 94.78* 0.23
   2 9969 7.2334902E+01 7.21E+01 99.67 99.51 0.06
   3 9953 2.0031220E+01 1.98E+01 99.02 98.78* 7.01
   4 9935 3.0243191E+02 3.01E+02 99.49 99.17 0.08
   5 9923 1.4045625E+00 4.07E-01 28.98 28.87* 0.10
   6 9908 9.0281350E+04 9.02E+04 99.90 99.44 0.04
   7 9889 3.1130477E+03 2.03E+03 65.10 64.74* 0.06
   8 9870 1.3674844E+04 9.62E+03 70.31 69.86 0.06
   9 9854 1.3789559E+04 5.73E+03 41.59 41.28* 0.08
  10 9836 2.1660894E+06 1.50E+06 69.24 68.67 0.07
|-----------------------------------------------------------------------------|
  10 99119 1.4419203E+00 3.98E-01 27.62 86.97 0.07 1.80 10
|-----------------------------------------------------------------------------|
  11 19980 1.1593664E+05 4.68E+04 40.37 57.06* 0.04
  12 19980 8.0033169E+05 4.02E+05 50.25 71.03 0.03
  13 19980 5.8890347E+05 3.50E+05 59.38 83.93 0.02
  14 19980 8.1370038E+06 7.72E+06 94.86 134.08 0.02
  15 19980 4.8533180E+06 3.47E+06 71.57 101.17* 0.01
|-----------------------------------------------------------------------------|
  15 99900 1.3425386E+05 4.61E+04 34.32 108.49 0.01 1.88 5
|=============================================================================|
| Time estimate for generating 10000 events: 0d:03h:00m:03s
| Starting simulation for process 'eehvv'
| Simulate: using integration grids from file 'eehvv.m1.vg'
| RNG: Initializing TAO random-number generator
| RNG: Setting seed for random-number generator to 4551
| Simulation: requested number of events = 0
| corr. to luminosity [fb-1] = 0.0000E+00
| Events: reading from raw file 'eehvv.evx'
| Events: parameter mismatch, discarding old event set
| Events: closing raw file 'eehvv.evx'
| Events: generating new events
| Events: writing to raw file 'eehvv.evx'
| Events: generating 0 unweighted, unpolarized events ...
| Events: event normalization mode '1'
| ... event sample complete.
| Events: closing raw file 'eehvv.evx'
eehvv:
   1.3425386E+05 +- 4.61E+04 fb ( 34. %)
| There were no errors and 20 warning(s).
| WHIZARD run finished.

this was the code,

model = z2btype2UFO (ufo)

Ma = 50 GeV
betaH = 1.40564765
process eeaavv = e1 , e1bar => nu1:nu2:nu3, nu1bar:nu2bar:nu3bar, a, a

sqrts = 250 GeV
beams = e1 , e1bar #=> isr

?fatal_beam_decay = false

isr_q_max = 20 GeV
isr_alpha = 1./137.
epa_q_min = 5 GeV
epa_x_min = 0.01

compile

!!beams_pol_density = @(-1), @(+1)
!!beams_pol_fraction = 80%, 30%

integrate (eeaavv)

simulate (eeaavv)
show (results)

Any insight into this would be much appreciated.

Hi Tabira,
Whizard issues warning that could guide you (hopefully) to a solution for your problem. Here this was:
Warning: Intermediate decay of zero-width particle h2 may be possible.
h2 in your setup is the 125 GeV Higgs state, however, it's width is set to zero. This means that there is a propagator with an explicit pole, and the Monte Carlo adapts to this singularity. For this reason, your cross section was rising from iteration to iteration. If I just
send a ballpark value for the width of
Wh2 = 4 MeV
in the SINDARIN, I get a nicely converging result with a sensible cross section prediction:
|=============================================================================|
| It Calls Integral[fb] Error[fb] Err[%] Acc Eff[%] Chi2 N[It] |
|=============================================================================|
| VAMP: parameter mismatch, discarding grid file 'eeaavv.m1.vg'
   1 9976 3.2889874E+00 6.38E-02 1.94 1.94* 12.14
   2 9952 3.2426264E+00 2.33E-02 0.72 0.72* 29.05
   3 9932 3.2483720E+00 1.57E-02 0.48 0.48* 40.66
   4 9907 3.2539005E+00 1.30E-02 0.40 0.40* 44.05
   5 9883 3.2223386E+00 1.25E-02 0.39 0.38* 41.08
   6 9859 3.2427026E+00 1.25E-02 0.39 0.38* 38.30
   7 9834 3.2313777E+00 1.30E-02 0.40 0.40 35.02
   8 9807 3.2560449E+00 1.32E-02 0.41 0.40 34.56
   9 9781 3.2479421E+00 1.33E-02 0.41 0.40 35.43
  10 9756 3.2521683E+00 1.34E-02 0.41 0.41 35.22
|-----------------------------------------------------------------------------|
  10 98687 3.2439769E+00 4.57E-03 0.14 0.44 35.22 0.72 10
|-----------------------------------------------------------------------------|
  11 19977 3.2473853E+00 9.57E-03 0.29 0.42 30.41
  12 19977 3.2510866E+00 9.49E-03 0.29 0.41* 28.68
  13 19977 3.2344789E+00 9.55E-03 0.30 0.42 27.15
  14 19977 3.2421897E+00 9.34E-03 0.29 0.41* 26.09
  15 19977 3.2601169E+00 9.58E-03 0.29 0.42 24.74
|-----------------------------------------------------------------------------|
  15 99885 3.2470012E+00 4.25E-03 0.13 0.41 24.74 1.01 5
|=============================================================================|
Best,
   JRR

Thanks a lot. The warning unfortunately skipped my notice. One more question, so now I am attempting ee > vvXXA, so I introduced the cuts in the following way,

cuts = any Pt >= 5 GeV and Theta > 7 degree and Theta < 173 degree [A]
        and
        any E > 10 GeV [A]

and whizard generated,

| Phase space: 201 channels, 11 dimensions
| Phase space: found 201 channels, collected in 41 groves.
| Phase space: Using 434 equivalences between channels.
| Phase space: wood
| Beam structure: isr, none => none, isr
| Beam structure: 1 channels, 2 dimensions
| Applying user-defined cuts.
| Starting integration for process 'eeaavvA'
| Integrate: iterations not specified, using default
| Integrate: iterations = 10:20000:"gw", 5:50000:""
| Integrator: 41 chains, 201 channels, 13 dimensions
| Integrator: Using VAMP channel equivalences
| Integrator: 20000 initial calls, 20 bins, stratified = T
| Integrator: VAMP
|=============================================================================|
| It Calls Integral[fb] Error[fb] Err[%] Acc Eff[%] Chi2 N[It] |
|=============================================================================|
| VAMP: parameter mismatch, discarding grid file 'eeaavvA.m1.vg'
   1 19899 1.5251495E-01 1.48E-02 9.71 13.70* 3.14
   2 19739 1.4028564E-01 2.97E-03 2.12 2.97* 3.47
   3 19589 1.4021941E-01 1.96E-03 1.40 1.96* 4.22
   4 19444 1.4255784E-01 1.68E-03 1.18 1.64* 5.47
   5 19320 1.4347904E-01 1.71E-03 1.19 1.65 5.79
   6 19193 1.4252966E-01 1.37E-03 0.96 1.34* 8.97
   7 19087 1.4102041E-01 1.26E-03 0.90 1.24* 11.30
   8 18992 1.4208468E-01 1.39E-03 0.98 1.35 7.49
   9 18897 1.4160934E-01 1.29E-03 0.91 1.25* 9.50
  10 18807 1.4040530E-01 1.21E-03 0.86 1.19* 10.99
|-----------------------------------------------------------------------------|
  10 192967 1.4162529E-01 4.98E-04 0.35 1.55 10.99 0.50 10
|-----------------------------------------------------------------------------|
  11 49973 1.3889819E-01 7.42E-04 0.53 1.19 8.58
  12 49973 1.4021139E-01 7.42E-04 0.53 1.18* 7.51
  13 49973 1.3943341E-01 7.38E-04 0.53 1.18* 6.95
  14 49973 1.4050985E-01 7.30E-04 0.52 1.16* 6.77
  15 49973 1.3877765E-01 7.42E-04 0.53 1.20 6.14
|-----------------------------------------------------------------------------|
  15 249865 1.3957179E-01 3.30E-04 0.24 1.18 6.14 1.10 5
|=============================================================================|
| Time estimate for generating 10000 events: 0d:00h:01m:53s
| Starting simulation for process 'eeaavvA'
| Simulate: using integration grids from file 'eeaavvA.m1.vg'
| RNG: Initializing TAO random-number generator
| RNG: Setting seed for random-number generator to 17355
| Simulation: requested number of events = 0
| corr. to luminosity [fb-1] = 0.0000E+00
| Events: reading from raw file 'eeaavvA.evx'
| Events: parameter mismatch, discarding old event set
| Events: closing raw file 'eeaavvA.evx'
| Events: generating new events
| Events: writing to raw file 'eeaavvA.evx'
| Events: generating 0 unweighted, unpolarized events ...
| Events: event normalization mode '1'
| ... event sample complete.
| Events: closing raw file 'eeaavvA.evx'
eeaavvA:
   1.3957179E-01 +- 3.30E-04 fb ( 0.24 %)
| WHIZARD run finished.

I am not sure if this correct. So I wanted to ask, is this an expected output for the cuts I have set? or should I make adjustments? Thank you in advance!

Thank you so much for your response. I know what to do now!