User Tools

Site Tools


Sidebar

Les Houches

2019 Session

Wikis of Previous sessions

Les Houches Themes

Help

2015:groups:sm:nloew

NLO EW technical comparisons

If you are interested in contributing please subscribe to the mailing list. You will be asked to log in with your CERN account. If you don't have a CERN account, please fill this form to create a lightweight account.

Working plan:

1) Summary of codes for EW automation

 Contributions from GOSAM, MadGraph5_aMC@NLO, OPENLOOPS, Recola, ...

2) Technical comparison of EW NLO cross sections

 Processes:  pp -> lljj     arXiv:1411.0916,   table 3 (and optionally table 4)
                                         and some related cumulative histograms
                            contributers (contact persons): 
                              Recola (denner@physik.uni-wuerzburg.de) 
                              OPENLOOPS (lindert@physik.uzh.ch)
                              ...
 
             pp -> lvjj     arXiv:1412.5157    table 3
                            contributers (contact persons): 
                              OPENLOOPS (lindert@physik.uzh.ch), 
                              MadGraph5_aMC@NLO?, 
                              GOSAM (nicolas.greiner@desy.de)
                              ...
             
             pp -> ttH      arXiv:1504.03446   table 3/4  for 13 TeV (or more energies)
                            contributers (contact persons):
                              MadGraph5_aMC@NLO (davide.pagani@uclouvain.be)
                              OPENLOOPS (lindert@physik.uzh.ch) 
                                ...

3) Comparison of Sudakov approximation with EW NLO corrections for distributions

 Processes:  pp -> lljj     arXiv:1411.0916,   table 3 and/or 4
                            contributers (contact persons): 
                            Recola (denner@physik.uni-wuerzburg.de) 
                            Chiesa et al. (mauro.chiesa@pv.infn.it; 
                                           fulvio.piccinini@pv.infn.it) 
                            Sherpa (jennifer.thompson@durham.ac.uk)
                             
             pp -> lvjj     arXiv:1412.5157    table 3
                            contributers (contact persons): 
                            OPENLOOPS (lindert@physik.uzh.ch) 
                            Chiesa et al. (mauro.chiesa@pv.infn.it; 
                                           fulvio.piccinini@pv.infn.it)
                            Sherpa (jennifer.thompson@durham.ac.uk)

4) Calculation of the ratio for sigma(pp -> Z/gamma*+jets)/sigma(pp -> gamma+jets) and comparison to data

    contributors (contact persons): 
      CMS (vitaliano.ciulli@cern.ch)
      OPENLOOPS (lindert@physik.uzh.ch)  
      Chiesa et al. (mauro.chiesa@pv.infn.it;
                     fulvio.piccinini@pv.infn.it)
      Sherpa (jennifer.thompson@durham.ac.uk)

Parameters according to CMS paper arXiv.1505.06250, now published JHEP 10 (2015) 128

NEW! Link to the Rivet analysis file and plots (last updated 01-03-2016):cms_2015_i1372730_v2.tar

  • There are three plugins:
    • CMS_2015_I1372730_Z: Z only plots
    • CMS_2015_I1372730_G: gamma only plots
    • CMS_2015_I1372730: all plots including ratios
  • the plugin with the ratio plots can only be run on a sample with both Z and gamma events with correct relative cross-section
  • otherwise to get the ratio plots one should run the first two plugins and then make the ratio (will try to provide a script, but just send the plots to vitaliano.ciulli@cern.ch and I will do it)

Selection cuts for the ratio plots:

  • For $Z/\gamma^{*}$ plus jets events we select:
    • two same flavour opposite sign leptons with $p_{T} > 20$ GeV and $|\eta| < 2.4$ and $71 < M_{\ell\ell} < 111 $ GeV and $p_{T}^{\ell\ell} > 100$ GeV
    • leptons are “dressed” with all photons in a cone of radius $\Delta R = 0.1$
    • at least one jet, jet selection $p_{T} > 30$ GeV and $|\eta| < 2.4$, we remove jets within a radius of $\Delta R < 0.5$ with respect to the axes of each lepton
    • for the ratio plots a cut on Z rapidity |y|<1.4 is also applied
  • For $\gamma$ plus jets events we select:
    • at least a prompt photon with $p_{T} > 100$ GeV and $|\eta| < 1.4$ (in case there is more than one photon the leading one satisfying all cuts is used)
    • the photon must be isolated, i.e. the scalar sum of the $p_T$ of all stable particle in a cone of radius $\Delta R = 0.4$ is less then 5 GeV
    • at least one jet, jet selection $p_{T} > 30$ GeV and $|\eta| < 2.4$ , we remove jets within a radius of $\Delta R < 0.5$ with respect to the axis of the photon

A Rivet analysis is being prepared to provide direct comparison with data at full particle level

Plots for the ratio:

  • Z boson differential transverse momentum cross-section in an inclusive $Z/\gamma^{*}+\mathrm{jets}$
  • $\gamma$ differential transverse momentum cross-section in an inclusive $\gamma+\mathrm{jets}$

in the following kinematic ranges:

  • $N_{jets} \geq1$
  • $N_{jets} \geq2$
  • $N_{jets} \geq3$
  • $H_{T} > 300$ GeV, $N_{\mathrm{jets}}\geq 1$

Points open for discussion/inputs:

  • are scale uncertainties correlated among the two processes?
  • is someone interested in having a Rivet routine which runs at parton level?

Comparison of LO + approx EWK (M. Chiesa et al) to CMS Z/gamma ratio:

Input parameters

as defined in the relevant papers:
Parameters etc. lljj lvjj ttH
order of LO contribution all all O(alphas2 alpha) and O(alphas alpha2)
order of NLO corrections O(alpha3 alphas2)O(alpha2 alphas3) and O(alpha3 alphas2) NLO EW O(alphas2 alpha2) and NLO QCD
renormalisation scheme G_mu scheme G_mu scheme alpha(MZ)
complex/real masses complex-mass scheme complex-mass scheme real masses
jet algorithm anti-kT R=0.4 anti-kT R=0.4 -
partons clustered for abs(y) < 5 abs(y) < infinity -
photon/jet separation democratic clustering+ fragmentation fermion-photon recombination and democratic clustering -
MAX(E_gamma/(E_gamma+E_jet) 0.7 0.5 -
PDFs MSTW2008LO PDF NNPDF2.3QED PDF NNPDF2.3QED PDF
factorization scale MZ_pole Hhat_T / 2 (scalar sum of all partonic E_T) H_T / 2
renormalization scale MZ_pole Hhat_T / 2 (scalar sum of all partonic E_T) H_T / 2
partons at LO g,u,c,d,s,b g,u,c,d,s,b,gamma g,u,c,d,s,b,gamma
partons at NLO g,u,c,d,s g,u,c,d,s,b g,u,c,d,s,b,gamma
gamma-induced contributions none only at LO all and none (PDF set to zero)
collider energy[TeV] 13 13 13
alpha_s from PDFs, 0.139395.. from PDF, 0.118 from PDF, 0.118
G_mu 1.1663787e-5 GeV**-2 1.16637e-5 from alpha
alpha calculated from G_mu calculated from G_mu 1/128.93
MZ_onshell 91.1876 GeV 91.1876 GeV 91.188 GeV
GZ_onshell 2.4952 GeV 2.4955 GeV 0 GeV
MZ_pole, GZ_pole calculated - -
MW_onshell 80.385 GeV 80.385 GeV 80.385 GeV
GW_onshell 2.085 GeV 2.0897 GeV 0 GeV
MW_pole, GW_pole calculated - -
complex masses defined from pole masses defined from on-shell masses -
mb 0 GeV 0 GeV 0 GeV
mt 173.2 GeV 173.2 173.3 GeV
Gamma_t 0 GeV 1.339 0 GeV
MH 125 GeV 125 GeV 125 GeV
Gamma_H 0 GeV 4.07 MeV 0 GeV
basic cuts pt_j > 30 GeV pt_j > 30 GeV
abs(y_j) < 4.5 abs(eta_j) < 4.5
pt_l > 20 GeV pt_l > 25 GeV
abs(y_l) < 2.5 abs(eta_l) < 2.5
dR_ll > 0.2 dR_jl > 0.5
dR_jl > 0.5 M_TW > 40 GeV
66 GeV < M_ll < 116 GeV missing_ET > 25 GeV
cumulative histogram 1 pT(j1) > 0.25,0.5,0.75,1 TeV pT(j1) > 0.5, 1 TeV pt(H) and pt(t) and pt(tbar) > 200 GeV
cumulative histogram 2 M_jj > 0.50,1,2,4 TeV missing_ET > 0.5, 1 TeV pt(H) and pt(t) and pt(tbar) > 400 GeV
cumulative histogram 3 pT(l-) > 0.25,0.5,0.75,1 TeV pT(l) > 0.5, 1 TeV pt(H) > 500 GeV
cumulative histogram 4 pT(ll) > 0.25,0.5,0.75,1 TeV abs( y(t) ) > 2.5
cumulative histogram 5 HT > 0.50,1,1.5,2 TeV HT > 0.5,1,2 TeV

Alternative lljj analysis: same as above with M_ll cut replaced by the following VBF cuts: M_jj > 600 GeV; abs(y_j1-y_j2) < 4.5; y_j1 * y_j2 < 0; min(y_j1,y_j2) < y_l < max(y_j1,y_j2).

2015/groups/sm/nloew.txt · Last modified: 2016/03/01 18:04 by vitaliano.ciulli