Question about Sh_2214_Wmunu_maxHTpTV2_CFilterBVeto

ATLAS Datasets
1

The metadata for evtgen dataset 700781 reads as follows:
{‘dataset_number’: ‘700781’,
‘physics_short’: ‘Sh_2214_Wmunu_maxHTpTV2_CFilterBVeto’,
‘e_tag’: None,
‘cross_section_pb’: 22935.0,
‘genFiltEff’: 0.1484349,
‘kFactor’: 1.0,
‘nEvents’: 49999391,
‘sumOfWeights’: None,
‘sumOfWeightsSquared’: None,
‘process’: None,
‘generator’: ‘Sherpa’,
‘keywords’: [‘Baseline’, ‘jets’, ‘muon’, ‘nlo’, ‘sm’, ‘w’],
‘description’: ‘Sherpa W+/W- → mu nu + 0,1,2j@NLO + 3,4,5j@LO with c-jet filter taking input from existing unfiltered input file.’,
‘job_path’: ‘Files · master · atlas-physics / pmg / MC Job Options · GitLab,
‘CoMEnergy’: 13600.0,
‘GenEvents’: 373518577,
‘GenTune’: ‘NULL’,
‘PDF’: ‘NULL’,
‘Release’: ‘AthGeneration_23.6.3’,
‘Filters’: ‘HeavyFlavorHadronFilter’,
‘cross_section_uncertainty’: 0.0,
‘hepmc_version’: 2,
‘release’: {‘name’: ‘2025r-evgen-13p6tev’}}
I’m still a little confused as to what this dataset contains because I’m not sure about the abbreviations in the physics_short description (and the job_path python file listed doesn’t help). Is this just W+c, with the c (mesons) decaying muonically, and the genFiltEfficiency taking into account both the c-jet filter efficiency and branching fraction for the c-meson muonic decay? Or am I interpreting this incorrectly?

2

Hi @rakhi ,

I’ve got some more documentation of the physics shorts in review now, so I hope it’ll be a little better soon. Breaking this one down:

  • Sh: Sherpa
  • 2214: Sherpa version 2.2.14
  • Wmunu: W bosons decaying to mu neutrino (it’s the W decay specifically that we’re talking about here)
  • maxHTpTV2: the sample is biased based on the maximum of the HT and the pT of the vector boson. Biasing means that the unweighted spectrum of events has more high-energy events, so that we have better statistical uncertainties at high energies (high HT / pTV here). That allows us to generate a single sample that has good statistics across the entire spectrum, rather than needing separate samples for measurements interested in the bulk of the cross section and for searches that are interested in tails.
  • CFilterBVeto: the matrix elements are required to have at least one c-quark and no b-quark. Similarly, BFilter means at least one b-quark in the matrix element, and CVetoBVeto means no b-quark or c-quark in the matrix element.

I hope that helps!

Best,
Zach

3

Thanks Zach, that’s very helpful. (Assume in the final sentence you meant either “CVetoBVeto” or" “at least one b-quark and at least one c-quark in the matrix element”?)

Any chance we can lay our hands on an alternate set where the c-meson decays muonically too? Some collaborators and I are trying to estimate the FNP background for a dimuon search using the fake factor method, and this would likely be our leading background.

4

Hi @rakhi ,

Sorry, yes — I’ve edited the post above to be correct. The new documentation is live, btw:

I’m not sure if we have an inclusive sample like the one you’re describing. We’ve got this that’s included in the 13 TeV open data:

(‘300005’, ‘Pythia8B_AU2_CTEQ6L1_JpsimumuWmunu’)

I’m not sure I see something even internally that’s what you’re after, but I’ll ask around in case I’ve missed it.

Best,
Zach

5

And now the second part of the answer: yes! I just had to learn about the sample.

{'dataset_number': '501719',
 'physics_short': 'MGPy8EG_Wmunu_FxFx_3jets_HT2bias_SMT',
 'e_tag': None,
 'cross_section_pb': 22165.0,
 'genFiltEff': 0.003464519,
 'kFactor': 1.0,
 'nEvents': 10000000,
 'sumOfWeights': None,
 'sumOfWeightsSquared': None,
 'process': None,
 'generator': 'aMcAtNlo+Pythia8(v.245p3.lhcb7)+EvtGen(v.1.7.0)',
 'keywords': ['Specialised', 'jets', 'muon', 'nlo', 'sm', 'w'],
 'description': 'aMcAtNlo Wmunu+0,1,2,3j NLO FxFx HT2-biased SMT Filter',
 'job_path': 'https://gitlab.cern.ch/atlas-physics/pmg/mcjoboptions/-/blob/master/501xxx/501719/mc.MGPy8EG_Wmunu_FxFx_3jets_HT2bias_SMT.py',
 'CoMEnergy': 13000.0,
 'GenEvents': 181210500,
 'GenTune': 'A14 NNPDF23LO',
 'PDF': 'NULL',
 'Release': 'AthGeneration_21.6.80',
 'Filters': 'MuonFilter, MultiMuonFilter',
 'cross_section_uncertainty': 0.0,
 'hepmc_version': 2,
 'release': {'name': '2025r-evgen-13tev'}}

The MultiMuonFilter was the hint. SMT (in the name of the sample) is for “soft muon tagger”, developed for this paper. It requires one muon above 15 GeV (which will be the one from the W most of the time) and a second muon above 3.25 GeV (which will be from a b or c decay most of the time).

We’ve only got that sample at 13 TeV at the moment.

Best,
Zach

6

fabulous!!! Thank you Zach!