Rivet analyses

title: D0_2010_I871787

Precise study of Z pT using novel phi* technique

Experiment: D0 (Tevatron Run 2)

Inspire ID: 871787

Status: VALIDATED

Authors: - Frank Siegert

References: - arXiv: 1010.0262

Beams: p- p+

Beam energies: (980.0, 980.0)GeV

Run details: - Inclusive $Z/\gamma^*$ production in both electron and muon channels. Cut on invariant lepton mass should be wider than $70 < m_{\ell\ell} < 110$ GeV.

Using 7.3 pb$^{-1}$ the distribution of the variable $\phi^$ is measured, which probes the same physical effects as the $Z/\gamma^$ boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. Results are presented for both the di-electron and di-muon channel.

Source code:D0_2010_I871787.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DileptonFinder.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

/// Precise study of Z pT using novel phi* technique class D0_2010_I871787 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(D0_2010_I871787);


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

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

  /// Initialise and register projections
  FinalState fs;
  Cut cuts_e = (Cuts::abseta < 1.1 || Cuts::absetaIn(1.5, 3.0)) && Cuts::pT > 20 * GeV;
  DileptonFinder zfinder_ee(91.2 * GeV, 0.2, cuts_e && Cuts::abspid == PID::ELECTRON,
                            Cuts::massIn(70 * GeV, 110 * GeV));
  declare(zfinder_ee, "zfinder_ee");
  Cut cuts_m = Cuts::abseta < 2 && Cuts::pT > 15 * GeV;
  DileptonFinder zfinder_mm(91.2 * GeV, 0.0, cuts_m && Cuts::abspid == PID::MUON,
                            Cuts::massIn(70 * GeV, 110 * GeV));
  declare(zfinder_mm, "zfinder_mm");

  /// Book histograms here
  book(_h_phistar_ee, {0., 1., 2., 10.}, {"d01-x01-y01", "d01-x01-y02", "d01-x01-y03"});
  book(_h_phistar_mm, {0., 1., 2.}, {"d02-x01-y01", "d02-x01-y02"});
}


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

  const DileptonFinder& zfinder_ee = apply<DileptonFinder>(event, "zfinder_ee");
  if (zfinder_ee.bosons().size() == 1) {
    Particles ee = zfinder_ee.constituents();
    std::sort(ee.begin(), ee.end(), cmpMomByPt);
    const FourMomentum& eminus = PID::charge3(ee[0].pid()) < 0 ? ee[0].momentum() : ee[1].momentum();
    const FourMomentum& eplus = PID::charge3(ee[0].pid()) < 0 ? ee[1].momentum() : ee[0].momentum();
    double phi_acop = M_PI - mapAngle0ToPi(eminus.phi() - eplus.phi());
    double costhetastar = tanh((eminus.eta() - eplus.eta()) / 2);
    double sin2thetastar = 1 - sqr(costhetastar);
    if (sin2thetastar < 0) sin2thetastar = 0;
    const double phistar = tan(phi_acop / 2) * sqrt(sin2thetastar);
    const FourMomentum& zmom = zfinder_ee.bosons()[0].momentum();
    _h_phistar_ee->fill(zmom.rapidity(), phistar);
  }

  const DileptonFinder& zfinder_mm = apply<DileptonFinder>(event, "zfinder_mm");
  if (zfinder_mm.bosons().size() == 1) {
    Particles mm = zfinder_mm.constituents();
    std::sort(mm.begin(), mm.end(), cmpMomByPt);
    const FourMomentum& mminus = PID::charge3(mm[0].pid()) < 0 ? mm[0].momentum() : mm[1].momentum();
    const FourMomentum& mplus = PID::charge3(mm[0].pid()) < 0 ? mm[1].momentum() : mm[0].momentum();
    double phi_acop = M_PI - mapAngle0ToPi(mminus.phi() - mplus.phi());
    double costhetastar = tanh((mminus.eta() - mplus.eta()) / 2);
    double sin2thetastar = 1 - sqr(costhetastar);
    if (sin2thetastar < 0) sin2thetastar = 0;
    const double phistar = tan(phi_acop / 2) * sqrt(sin2thetastar);
    const FourMomentum& zmom = zfinder_mm.bosons()[0].momentum();
    _h_phistar_mm->fill(zmom.rapidity(), phistar);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize({_h_phistar_ee, _h_phistar_mm});
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DGroupPtr _h_phistar_ee, _h_phistar_mm;
/// @}

};

RIVET_DECLARE_ALIASED_PLUGIN(D0_2010_I871787, D0_2010_S8821313);

} ```

Aliases: - D0_2010_S8821313