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CDF_2000_S4155203

Z pT measurement in CDF Z -> $e^+e^-$ events
Experiment: CDF (Tevatron Run 1)
Inspire ID: 505738
Status: VALIDATED
Authors:
  • Hendrik Hoeth
References: Beams: p- p+
Beam energies: (900.0, 900.0) GeV
Run details:
  • $p\bar{p}$ collisions at 1800 GeV. $Z/\gamma^*$ Drell-Yan events with $e^+e^-$ decay mode only. Restrict $Z/\gamma^*$ mass range to roughly $50 \text{GeV}/c^2 < m_{ee} < 120 \text{GeV}/c^2$ for efficiency.

Measurement of transverse momentum and total cross section of $e^+e^-$ pairs in the Z-boson region of $66 \text{GeV}/c^2 < m_{ee} < 116 \text{GeV}/c^2$ from pbar-p collisions at $\sqrt{s} = 1.8$ TeV, with the Tevatron CDF detector. The $Z$ $p_\perp$, in a fully-factorised picture, is generated by the momentum balance against initial state radiation (ISR) and the primordial/intrinsic $p_\perp$ of the $Z$'s parent partons in the incoming hadrons. The $Z$ $p_\perp$ is important in generator tuning to fix the interplay of ISR and multi-parton interactions (MPI) in generating `underlying event' activity. This analysis is subject to ambiguities in the experimental Z pT definition, since the Rivet implementation reconstructs the Z momentum from the dilepton pair with finite cones for QED bremstrahlung summation, rather than non-portable direct use of the (sometimes absent) Z in the event record.

Source code: CDF_2000_S4155203.cc 
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ZFinder.hh"

namespace Rivet {


  /// @brief CDF Run I Z \f$ p_\perp \f$ in Drell-Yan events
  ///
  /// @author Hendrik Hoeth
  class CDF_2000_S4155203 : public Analysis {
  public:

    RIVET_DEFAULT_ANALYSIS_CTOR(CDF_2000_S4155203);


    /// @name Analysis methods
    //@{

    void init() {
      // Set up projections
      ZFinder zfinder(FinalState(), Cuts::open(), PID::ELECTRON,
                      66*GeV, 116*GeV, 0.0, ZFinder::ClusterPhotons::NONE);
      declare(zfinder, "ZFinder");

      // Book histogram
      book(_hist_zpt ,1, 1, 1);
    }


    /// Do the analysis
    void analyze(const Event& e) {
      const ZFinder& zfinder = apply<ZFinder>(e, "ZFinder");
      if (zfinder.bosons().size() != 1) {
        MSG_DEBUG("Num e+ e- pairs found = " << zfinder.bosons().size());
        vetoEvent;
      }

      FourMomentum pZ = zfinder.bosons()[0].momentum();
      if (pZ.mass2() < 0) {
        MSG_DEBUG("Negative Z mass**2 = " << pZ.mass2()/GeV2 << "!");
        vetoEvent;
      }

      MSG_DEBUG("Dilepton mass = " << pZ.mass()/GeV << " GeV");
      MSG_DEBUG("Dilepton pT   = " << pZ.pT()/GeV << " GeV");
      _hist_zpt->fill(pZ.pT()/GeV);
    }


    void finalize() {
      scale(_hist_zpt, crossSection()/picobarn/sumOfWeights());
    }

    //@}


  private:

    Histo1DPtr _hist_zpt;

  };



  RIVET_DECLARE_ALIASED_PLUGIN(CDF_2000_S4155203, CDF_2000_I505738);

}