Rivet analyses

title: CMS_2013_I1272853

Study of observables sensitive to double parton scattering in $W + 2$ jets process in $pp$ collisions at $\sqrt{s} = 7$~TeV

Experiment: CMS (LHC)

Inspire ID: 1272853

Status: VALIDATED

Authors: - Sunil Bansal

References: - Expt page: CMS-FSQ-12-028 - CERN-PH-EP-2013-224 - arXiv: 1312.5729 - Submitted to JHEP

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - Only muonic decay of W boson

Double parton scattering is investigated in proton-proton collisions at $\sqrt{s} = 7$~TeV where the final state includes a $W$ boson, which decays into a muon and a neutrino, and two jets. The data sample corresponds to an integrated luminosity of 5 inverse femtobarns, collected with the CMS detector at the LHC.

Source code:CMS_2013_I1272853.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

include "Rivet/Projections/InvMassFinalState.hh"

include "Rivet/Projections/LeadingParticlesFinalState.hh"

include "Rivet/Projections/MissingMomentum.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// CMS W + 2 jet double parton scattering analysis class CMS_2013_I1272853 : public Analysis { public:

/// Constructor
CMS_2013_I1272853()
    : Analysis("CMS_2013_I1272853") { }


/// Book histograms and initialise projections before the run
void init() {

  const FinalState fs;
  declare(fs, "FS");

  /// @todo Use C++11 initialisation syntax
  vector<PdgIdPair> vidsW;
  vidsW += make_pair(PID::MUON, PID::NU_MUBAR), make_pair(PID::ANTIMUON, PID::NU_MU);
  InvMassFinalState invfsW(fs, vidsW, 20 * GeV, 1e6 * GeV);
  declare(invfsW, "INVFSW");

  VetoedFinalState vfs(fs);
  vfs.addVetoOnThisFinalState(invfsW);
  declare(vfs, "VFS");
  declare(FastJets(vfs, JetAlg::ANTIKT, 0.5), "Jets");

  book(_h_deltaS_eq2jet_Norm, 1, 1, 1);
  book(_h_rel_deltaPt_eq2jet_Norm, 2, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {

  // Find Ws
  const InvMassFinalState& invMassFinalStateW = apply<InvMassFinalState>(event, "INVFSW");
  if (invMassFinalStateW.empty()) vetoEvent;
  const Particles& WDecayProducts = invMassFinalStateW.particles();
  if (WDecayProducts.size() < 2) vetoEvent;

  // Cuts on W decay properties
  const int iNU_MU = (WDecayProducts[1].abspid() == PID::NU_MU) ? 1 : 0;
  const int iAN_MU = 1 - iNU_MU;
  const double pt1 = WDecayProducts[iAN_MU].pT();
  const double pt2 = WDecayProducts[iNU_MU].Et();
  const double eta1 = WDecayProducts[iAN_MU].abseta();
  const double phi1 = WDecayProducts[iAN_MU].phi();
  const double phi2 = WDecayProducts[iNU_MU].phi();
  const double mt = sqrt(2 * pt1 * pt2 * (1 - cos(phi1 - phi2)));
  if (mt < 50 * GeV || pt1 < 35 * GeV || eta1 > 2.1 || pt2 < 30 * GeV) vetoEvent;

  // Get jets and make sure there are at least two of them in |y| < 2
  const FastJets& jetpro = apply<FastJets>(event, "Jets");
  vector<FourMomentum> jets;
  for (const Jet& jet : jetpro.jetsByPt(Cuts::pT > 20 * GeV && Cuts::abseta < 2.0)) {
    jets.push_back(jet.momentum());
  }
  if (jets.size() != 2) vetoEvent;

  const double mupx = pt1 * cos(phi1);
  const double mupy = pt1 * sin(phi1);
  const double met_x = pt2 * cos(phi2);
  const double met_y = pt2 * sin(phi2);
  const double dpt = add_quad(jets[0].px() + jets[1].px(), jets[0].py() + jets[1].py());
  const double rel_dpt = dpt / (jets[0].pT() + jets[1].pT());
  const double pT2 = sqr(mupx + met_x) + sqr(mupy + met_y);
  const double Px = (mupx + met_x) * (jets[0].px() + jets[1].px());
  const double Py = (mupy + met_y) * (jets[0].py() + jets[1].py());
  const double p1p2_mag = dpt * sqrt(pT2);
  const double dS = acos((Px + Py) / p1p2_mag);

  _h_rel_deltaPt_eq2jet_Norm->fill(rel_dpt);
  _h_deltaS_eq2jet_Norm->fill(dS);
}


/// Normalise histograms etc., after the run
void finalize() {
  const double rel_dpt_bw = 1.0002 / 30.0;
  const double dphi_bw = 3.14160 / 30.0;
  normalize(_h_rel_deltaPt_eq2jet_Norm, rel_dpt_bw);
  normalize(_h_deltaS_eq2jet_Norm, dphi_bw);
}

private:

Histo1DPtr _h_rel_deltaPt_eq2jet_Norm;
Histo1DPtr _h_deltaS_eq2jet_Norm;

};

RIVET_DECLARE_PLUGIN(CMS_2013_I1272853);

} ```