Les Houches

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====== NLO EW technical comparisons ======

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===== 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 [[http://arxiv.org/abs/1505.06520|arXiv.1505.06250]], now published [[http://dx.doi.org/10.1007/JHEP10(2015)128|JHEP 10 (2015) 128]] 
 
**NEW!** Link to the Rivet analysis file and plots (last updated 01-03-2016):{{:2015:groups:sm: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: 
  * {{:2015:groups:sm:rzg1_alpgen.pdf|V +>= 1 jet}}
  * {{:2015:groups:sm:rzg2_alpgen.pdf|V +>= 2 jet}}
  * {{:2015:groups:sm:rzg3_alpgen.pdf|V +>= 3 jet}} 

===== Input parameters =====

  as defined in the relevant papers:

^ Parameters etc.          ^ lljj                ^ lvjj                 ^  ttH              ^
| order of LO contribution | all                 | all                  |   O(alphas**2 alpha)  and O(alphas alpha**2)                |
| order of NLO corrections | O(alpha**3 alphas**2)|O(alpha**2  alphas**3) and O(alpha**3  alphas**2) | NLO EW O(alphas**2 alpha**2) 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).
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