LHC Electroweak Multiboson Subgroup: Monte Carlo comparison

This public page documents a Monte Carlo comparison within the Multiboson subgroup of the LHC electroweak group.

Objectives

  • Summarise and compare state-of-the-art Monte Carlo predictions for multiboson (VV, VVV, VBF-V, VBS) production.
  • Compare against nominal Monte Carlo samples in ATLAS / CMS.
  • Compare fixed-order (NNLO QCD and NLO EW) predictions with NLOPS predictions.
  • Compare different NLOPS matching/merging schemes and possibly quantify related systematic uncertainties.
  • Compare shower Monte Carlo programs with analytical resummation.
  • Based on available Rivet routines, however not limited to published results.

Considered processes and analyses

For every class of multiboson processes (VV, VVV, VBF-V, VBS) we consider one (or more) example processes. In particular we consider the following processes. The analyses are based on published Rivet analyses. However, they have been modified to incorporate additional observables. All analyses are available in the LHCEWWG git repository:

https://gitlab.cern.ch/lhcewkwg/lhcewkwg-multiboson/mc-comparison.git

VV

Process Mode based on contributing groups
$ Z\gamma$ $Z(\to e^+ e^-) \gamma$ ATLAS_2016_I1448301  
$ZZ$ $Z(\to \ell^+ \ell^-) Z(\to \ell'^+ \ell'^-) $ ATLAS_2015_I1394865 (line-shape) & CMS_2012_I1298807 (pTZZ) & MC_ZZINC  
$WW$ $W(\to e^+ \nu)W(\to e^- \bar\nu)$ ATLAS_2016_I1426515 & MC_WWINC & MC_WWJETS  
$WZ$ $W(\to \mu^+ \nu_{\mu})Z(\to e^+ e^-) $ ATLAS_2016_I1469071 &ATLAS_2016_I1492320_3  

Desired accuracy: 1) fixed order: NNLO QCD + NLO EW, NLO QCD for loop-induced gg, 2) NLOPS (0,1j merged)

VVV

Process Mode based on contributing groups
$WWW$ $W(\to e^+ \nu_e)W(\to e^- \bar\nu_e)W(\to \mu^{+} \nu_{\mu})$ ATLAS_2016_I1492320_3l  

Desired accuracy: 1) fixed order: NLO QCD, NLO EW (on-shell V), 2) NLOPS (0,1j merged optional)

VBF-V

Process Mode based on contributing groups
$Z+2j$ $Z(\to e^+ e^-) +2j$ ATLAS_2014_I1279489  

Desired accuracy: 1) fixed order: full SM, 2) NLOPS (in vbf approximation)

VBS

Process Mode based on contributing groups
$WW+2j$ $W^+W^++2j$ ATLAS_2014_I1298023 & MC_WWJETS  

Desired accuracy: 1) fixed order: full SM, 2) NLOPS (in vbf approximation)

Setups

General

  • $\sqrt{s}$ = 13TeV
  • PDF: NLO: NNPDF31_nlo_as_0118_luxqed, NNLO: NNPDF31_nlo_as_0118_luxqed
  • guideline for central scales (+ 7-pt scale variations):
      • VV/VVV: $\mu_R=\mu_F=1/2 \sum_{V} M^{V}_T+ 1/2 \sum_{i} p_{T,j_i}  $ with $M^{V_i}_T = \sqrt{p_{T,ll}^2 + m^2_{ll}} $
      • VBF/VBS: $\mu_R=\mu_F=1/2 \sum_{V} M^{V}_T+ 1/2*(p_{T,j_1} + p_{T,j_2})$

  Mass [Gev] Width [GeV]
MW 80.385 2.0854
MZ 91.1876 2.4952
Mt 173.2 1.339
Mh 125 0.00407

  • inclusive generation cuts: $ p_{T,\ell} > 5\, {\rm GeV} , m_{\ell^+\ell^-} > 10 \, {\rm GeV}, p_{T,\gamma} > 20\, {\rm GeV}, $ for fixed-order $Z\gamma$ production use smooth-cone isolation with $R=0.4, n=1, \epsilon=0.5$

Fixed-order

NLOPS

-- JonasLindert1 - 2018-03-05

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Topic revision: r8 - 2018-08-09 - JonasLindert1
 
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