Rivet analyses

title: CMS_2012_I1298807

Inclusive ZZ production cross section and constraints on anomalous triple gauge couplings at 8~TeV

Experiment: CMS (LHC)

Inspire ID: 1298807

Status: VALIDATED

Authors: - Alexander Savin - Ian Ross

References: - arXiv: 1406.0113

Beams: p+ p+

Beam energies: (4000.0, 4000.0)GeV

Run details: - ZZ production, leptonic Z decays

A measurement of the inclusive $ZZ$ production cross section and constraints on anomalous triple gauge couplings in proton-proton collisions at $\sqrt{s} = 8 TeV$ are presented. The analysis is based on a data sample, corresponding to an integrated luminosity of 19.6/fb, collected with the CMS experiment at the LHC. The measurements are performed in the leptonic decay modes $ZZ \to lll^\prime l^\prime$, where $l = e,\mu$ and $l^\prime = e, \mu, \tau$. The measured total cross section $ \sigma (pp \to ZZ) = 7.7 \pm 0.5~(\mathrm{stat}) + 0.5 -0.4~(\mathrm{syst}) \pm 0.4~(\mathrm{theo}) \pm 0.2~(\mathrm{lumi})~pb$, for both $Z$ bosons produced in the mass range $60 < m_Z < 120 \GeV$, is consistent with standard model predictions. Differential cross sections, in phase space $p_T(\mu) > 5 \GeV$, $p_T(e) > 7 \GeV$, $|\eta(\mu)|<2.4$ , $|\eta(e)|<2.5$ and the 60--120~\GeV mass requirement, are measured and well described by the theoretical predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous $ZZZ$ and $ZZ\gamma$ couplings at the 95\% confidence level, $-0.004 < f4Z < 0.004$, $-0.004 < f5Z < 0.004$, $-0.005 < f4\gamma < 0.005$, and $-0.005 < f5\gamma < 0.005.$

Source code:CMS_2012_I1298807.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/IdentifiedFinalState.hh"

include "Rivet/Projections/MergedFinalState.hh"

include "Rivet/Projections/VetoedFinalState.hh"

namespace Rivet {

/// Inclusive ZZ production cross section and constraints on anomalous triple gauge couplings class CMS_2012_I1298807 : public Analysis { public:

// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2012_I1298807);


/// Initialise projections and histograms
void init() {

  FinalState leptons((Cuts::abspid == PID::ELECTRON && Cuts::abseta < 2.5)
                     || (Cuts::abspid == PID::MUON && Cuts::abseta < 2.4));
  declare(leptons, "Leptons");

  Cut cut_el = Cuts::abseta < 2.5 && Cuts::pT > 7.0 * GeV;
  DileptonFinder zeefinder(91.2 * GeV, 0.1, cut_el && Cuts::abspid == PID::ELECTRON,
                           Cuts::massIn(60 * GeV, 120 * GeV));
  declare(zeefinder, "ZeeFinder");

  Cut cut_mu = Cuts::abseta < 2.4 && Cuts::pT > 5.0 * GeV;
  DileptonFinder zmmfinder(91.2 * GeV, 0.1, cut_mu && Cuts::abspid == PID::MUON,
                           Cuts::massIn(60 * GeV, 120 * GeV));
  declare(zmmfinder, "ZmmFinder");

  VetoedFinalState fs_woZmm;
  fs_woZmm.addVetoOnThisFinalState(zmmfinder);
  VetoedFinalState fs_woZee;
  fs_woZee.addVetoOnThisFinalState(zeefinder);

  DileptonFinder zeefinder_woZee(fs_woZee, 91.2 * GeV, 0.1, cut_el && Cuts::abspid == PID::ELECTRON,
                                 Cuts::massIn(60 * GeV, 120 * GeV));
  declare(zeefinder_woZee, "Zeefinder_WoZee");
  DileptonFinder zmmfinder_woZmm(fs_woZmm, 91.2 * GeV, 0.1, cut_mu && Cuts::abspid == PID::MUON,
                                 Cuts::massIn(60 * GeV, 120 * GeV));
  declare(zmmfinder_woZmm, "Zmmfinder_WoZmm");

  // Book histograms
  book(_h["pt_l1"], 1, 1, 1);
  book(_h["pt_z1"], 1, 1, 2);
  book(_h["pt_zz"], 1, 1, 3);
  book(_h["m_zz"], 1, 1, 4);
  book(_h["dphi_zz"], 1, 1, 5);
  book(_h["dR_zz"], 1, 1, 6);
}


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

  // Find leading leptons and apply cuts
  const Particles& leptons = apply<FinalState>(evt, "Leptons").particlesByPt();
  if (leptons.size() < 2) vetoEvent;
  const double leading_l_pt = leptons[0].pT();
  const double second_l_pt = leptons[1].pT();
  if (leading_l_pt < 20 * GeV || second_l_pt < 10 * GeV) vetoEvent;

  // Find acceptable ZZ combinations and build four-momenta, otherwise veto
  const DileptonFinder& zeefinder = apply<DileptonFinder>(evt, "ZeeFinder");
  const DileptonFinder& zeefinder_woZee = apply<DileptonFinder>(evt, "Zeefinder_WoZee");
  const DileptonFinder& zmmfinder = apply<DileptonFinder>(evt, "ZmmFinder");
  const DileptonFinder& zmmfinder_woZmm = apply<DileptonFinder>(evt, "Zmmfinder_WoZmm");

  FourMomentum pZ_a, pZ_b, pZ_1, pZ_2;
  FourMomentum pZZ, Z_a_l1, Z_a_l2, Z_b_l1, Z_b_l2;
  if (zeefinder.bosons().size() > 0 && zmmfinder.bosons().size() > 0) {
    pZ_a = zeefinder.boson();
    pZ_b = zmmfinder.boson();
    pZZ = pZ_a + pZ_b;
    pZ_1 = pZ_a;
    pZ_2 = pZ_b;
    Z_a_l1 = zeefinder.constituents()[0];
    Z_a_l2 = zeefinder.constituents()[1];
    Z_b_l1 = zmmfinder.constituents()[0];
    Z_b_l2 = zmmfinder.constituents()[1];
  }
  else if (zeefinder.bosons().size() > 0 && zeefinder_woZee.bosons().size() > 0) {
    pZ_a = zeefinder.boson();
    pZ_b = zeefinder_woZee.boson();
    pZZ = pZ_a + pZ_b;
    pZ_1 = pZ_a;
    pZ_2 = pZ_b;
    Z_a_l1 = zeefinder.constituents()[0];
    Z_a_l2 = zeefinder.constituents()[1];
    Z_b_l1 = zeefinder_woZee.constituents()[0];
    Z_b_l2 = zeefinder_woZee.constituents()[1];
  }
  else if (zmmfinder.bosons().size() > 0 && zmmfinder_woZmm.bosons().size() > 0) {
    pZ_a = zmmfinder.boson();
    pZ_b = zmmfinder_woZmm.boson();
    pZZ = pZ_a + pZ_b;
    pZ_1 = pZ_a;
    pZ_2 = pZ_b;
    Z_a_l1 = zmmfinder.constituents()[0];
    Z_a_l2 = zmmfinder.constituents()[1];
    Z_b_l1 = zmmfinder_woZmm.constituents()[0];
    Z_b_l2 = zmmfinder_woZmm.constituents()[1];
  }
  else {
    vetoEvent;
  }

  // Set ordered pT variables
  /// @todo Looks like there should be a nicer way than this
  double pt_l1 = Z_a_l1.pT();
  if (Z_a_l2.pT() > pt_l1) pt_l1 = Z_a_l2.pT();
  if (Z_b_l1.pT() > pt_l1) pt_l1 = Z_b_l1.pT();
  if (Z_b_l2.pT() > pt_l1) pt_l1 = Z_b_l2.pT();

  // Leading Z pT
  double pt_z1 = pZ_a.pT();
  if (pZ_b.pT() > pZ_a.pT()) {
    pt_z1 = pZ_b.pT();
    pZ_1 = pZ_b;
    pZ_2 = pZ_a;
  }

  // Fill histograms
  _h["pt_zz"]->fill(pZZ.pT() / GeV);
  _h["m_zz"]->fill(pZZ.mass() / GeV);
  _h["dphi_zz"]->fill(deltaPhi(pZ_a, pZ_b));
  _h["dR_zz"]->fill(deltaR(pZ_a, pZ_b, PSEUDORAPIDITY));
  _h["pt_z1"]->fill(pt_z1 / GeV);
  _h["pt_l1"]->fill(pt_l1 / GeV);
}


/// Scale histograms
/// @todo Why is it scaling by bin width twice??
void finalize() {

  for (auto& item : _h) {
    double area = 0.;
    for (auto& b : item.second->bins()) {
      b.scaleW(1.0 / b.xWidth());
      area += b.sumW() / b.dVol();
    }
    if (area) scale(item.second, 1.0 / area);
  }
}


/// Histograms
map<string, Histo1DPtr> _h;

};

RIVET_DECLARE_PLUGIN(CMS_2012_I1298807);

} ```