Rivet analyses

title: LHCB_2015_I1373300

Measurement of the forward $Z$ boson cross-section in $pp$ collisions at $\sqrt{s}=7 TeV$

Experiment: LHCB (LHC)

Inspire ID: 1373300

Status: VALIDATED

Authors: - Ilya Segal

References: - LHCB-PAPER-2015-001 - CERN-PH-EP-2015-102 - JHEP 08 (2015) 039 - DOI:10.1007/JHEP08(2015)039 - arXiv: 1505.07024

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - Forward $W$ boson production in $pp$ collisions at $\sqrt{s}=7 TeV$, $p_{T}>20 GeV/c$, $\eta\in[2.0, 4.5]$

A measurement of the production cross-section for $Z$ bosons that decay to muons. The data were recorded by the LHCb detector during pp collisions at a centre-of-mass energy of $7 TeV$. The cross-section is measured for muons in the pseudorapidity range $2.0 < \eta < 4.5$ with transverse momenta $p_{T}>20 GeV/c$. The dimuon mass is restricted to $60 < M_{\mu\mu} < 120 GeV/c^2$.

Source code:LHCB_2015_I1373300.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/LeptonFinder.hh"

namespace Rivet {

/// @brief Forward Z boson production in pp collisions at 7 TeV class LHCB_2015_I1373300 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2015_I1373300);


/// @name Analysis methods
///@{

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

  // Initialise and register projections
  Cut cuts = (Cuts::pT >= 20.0 * GeV && Cuts::absetaIn(2.0, 4.5) && Cuts::abspid == PID::MUON);
  DileptonFinder zFinder(91.2 * GeV, 0.0, cuts, Cuts::massIn(60 * GeV, 120 * GeV));
  DileptonFinder zFinder_Fsr(91.2 * GeV, 0.1, cuts, Cuts::massIn(60 * GeV, 120 * GeV));
  LeptonFinder wFinder(cuts, 0.0);
  LeptonFinder wFinder_Fsr(cuts, 0.1);
  declare(zFinder, "DileptonFinder");
  declare(zFinder_Fsr, "DileptonFinder_Fsr");
  declare(wFinder, "LeptonFinder");
  declare(wFinder_Fsr, "LeptonFinder_Fsr");

  // Book histograms
  book(_h_zProdRap, 1, 1, 1);
  book(_h_zProdPt, 2, 1, 1);
  book(_h_zProdPhi, 3, 1, 1);
  book(_h_wPlusProdEta, 4, 1, 1);
  book(_h_wMinusProdEta, 4, 1, 3);
  book(_h_zProdRap_Fsr, 1, 1, 3);
  book(_h_zProdPt_Fsr, 2, 1, 3);
  book(_h_zProdPhi_Fsr, 3, 1, 3);
  book(_h_wPlusProdEta_Fsr, 4, 1, 5);
  book(_h_wMinusProdEta_Fsr, 4, 1, 6);
  book(_h_wRatioEta, 5, 1, 1);
  book(_h_wChargeAsymEta, 6, 1, 1);
  book(_h_wRatioEta_Fsr, 5, 1, 2);
  book(_h_wChargeAsymEta_Fsr, 6, 1, 2);
}


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

  // Searching for Z bosons
  const DileptonFinder& z = apply<DileptonFinder>(event, "DileptonFinder");
  if (!z.empty() && z.bosons().size() == 1) {
    const FourMomentum zmom = z.bosons()[0].momentum();
    const Particle& muPlus = z.leptons()[0];
    const Particle& muMinus = z.leptons()[1];
    const double phi = tan(0.5 * (M_PI - deltaPhi(muPlus, muMinus)))
        / cosh(0.5 * deltaEta(muPlus, muMinus));
    _h_zProdRap->fill(zmom.absrap());
    _h_zProdPt->fill(zmom.pt() / GeV);
    _h_zProdPhi->fill(phi);
  }

  // Searching for Z bosons + FSR photon
  const DileptonFinder& z_Fsr = apply<DileptonFinder>(event, "DileptonFinder_Fsr");
  if (!z_Fsr.empty() && z_Fsr.bosons().size() == 1) {
    const FourMomentum zmom = z_Fsr.bosons()[0].momentum();
    const Particle& muPlus = z_Fsr.leptons()[0];
    const Particle& muMinus = z_Fsr.leptons()[1];
    const double phi = tan((M_PI - deltaPhi(muPlus, muMinus)) / 2) / cosh(deltaEta(muPlus, muMinus) / 2);
    _h_zProdRap_Fsr->fill(zmom.absrapidity());
    _h_zProdPt_Fsr->fill(zmom.pt() / GeV);
    _h_zProdPhi_Fsr->fill(phi);
  }

  // Searching for W bosons
  const DressedLeptons w = apply<LeptonFinder>(event, "LeptonFinder").dressedLeptons();
  if (w.size() > 0) {
    const Particle& mu = w[0];
    (mu.charge3() > 0 ? _h_wPlusProdEta : _h_wMinusProdEta)->fill(mu.abseta());
  }

  // Searching for W bosons + FSR photon
  const DressedLeptons w_Fsr = apply<LeptonFinder>(event, "LeptonFinder_Fsr").dressedLeptons();
  if (w_Fsr.size() > 0) {
    const Particle& mu = w_Fsr[0];
    (mu.charge3() > 0 ? _h_wPlusProdEta_Fsr : _h_wMinusProdEta_Fsr)->fill(mu.abseta());
  }
}


/// Normalise histograms etc., after the run
void finalize() {

  // Scaling of the histograms and correction on FSR
  const double xs = crossSection() / picobarn;
  const double sf = xs / sumOfWeights() / 2.0;

  scale(_h_zProdRap, sf);
  scale(_h_zProdRap_Fsr, sf);
  scale(_h_zProdPt, sf);
  scale(_h_zProdPt_Fsr, sf);
  scale(_h_zProdPhi, sf);
  scale(_h_zProdPhi_Fsr, sf);
  scale(_h_wPlusProdEta, sf);
  scale(_h_wPlusProdEta_Fsr, sf);
  scale(_h_wMinusProdEta, sf);
  scale(_h_wMinusProdEta_Fsr, sf);

  //Calculation of ratio and charge asymmetry
  divide(_h_wPlusProdEta, _h_wMinusProdEta, _h_wRatioEta);
  divide(_h_wPlusProdEta_Fsr, _h_wMinusProdEta_Fsr, _h_wRatioEta_Fsr);
  asymm(_h_wPlusProdEta, _h_wMinusProdEta, _h_wChargeAsymEta);
  asymm(_h_wPlusProdEta_Fsr, _h_wMinusProdEta_Fsr, _h_wChargeAsymEta_Fsr);
  scale(_h_wChargeAsymEta, 100);
  scale(_h_wChargeAsymEta_Fsr, 100);
}

///@}


/// @name Histograms
///@{
Histo1DPtr _h_zProdRap;
Histo1DPtr _h_zProdPt;
Histo1DPtr _h_zProdPhi;
Histo1DPtr _h_wPlusProdEta;
Histo1DPtr _h_wMinusProdEta;
Histo1DPtr _h_zProdRap_Fsr;
Histo1DPtr _h_zProdPt_Fsr;
Histo1DPtr _h_zProdPhi_Fsr;
Histo1DPtr _h_wPlusProdEta_Fsr;
Histo1DPtr _h_wMinusProdEta_Fsr;
Estimate1DPtr _h_wRatioEta;
Estimate1DPtr _h_wChargeAsymEta;
Estimate1DPtr _h_wRatioEta_Fsr;
Estimate1DPtr _h_wChargeAsymEta_Fsr;
///@}

};

RIVET_DECLARE_PLUGIN(LHCB_2015_I1373300);

} ```