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Rivet analyses reference

HRS_1990_I280958

$K^0$ spectrum in $e^+e^-$ collisions at 29 GeV
Experiment: HRS (PEP)
Inspire ID: 280958
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B205 (1988) 111-114
Beams: e+ e-
Beam energies: (14.5, 14.5) GeV
Run details:
  • Hadronic e+e- events at $\sqrt{s} = 29.$ GeV

$K^0$ meson momentum spectrum measured at $\sqrt{s} = 29.$ GeV using the HRS detector at PEP. The analysis includes flavour tagging by requiring either a single charged particle with $x_p>0.65 (light quarks) or a $D^{*+}$ meson (charm). The rapidities with respect to the chartged thrust axis are also included. The bin widths are not included in either the paper or HEPdata and have therefore been infered.

Source code: HRS_1990_I280958.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/Thrust.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class HRS_1990_I280958 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(HRS_1990_I280958);


    /// @name Analysis methods
    //@{

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

      // Initialise and register projections
      declare(Beam(), "Beams");
      declare(UnstableParticles(), "UFS");
      const ChargedFinalState cfs;
      declare(cfs, "CFS");
      declare(Thrust(cfs), "Thrust");

      // Book histograms
      book(_h_X        , 3, 1, 1);
      book(_h_rap_all  , 4, 1, 1);
      book(_h_rap_light, 6, 1, 1);
      book(_h_rap_charm, 5, 1, 1);
      book(_wLight,"TMP/wLight");
      book(_wCharm,"TMP/wCharm");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
      int nch = cfs.particles().size();
      if(nch<5) vetoEvent;
      // Get beams and average beam momentum
      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
      const double meanBeamMom = ( beams.first.p3().mod() +
                                   beams.second.p3().mod() ) / 2.0;
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
      // get the thrust axes
      const Thrust& thrust = apply<Thrust>(event, "Thrust");
      const Vector3 & axis = thrust.thrustAxis();
      // unstable particles
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      Particle pTag;
      // get the tags
      Particles Dstar = ufs.particles(Cuts::abspid==413);
      bool charmTagged = !Dstar.empty();
      if(charmTagged) {
	pTag = Dstar[0];
	for(const Particle & p : Dstar) {
	  if(p.E()>pTag.E()) pTag=p;
	}
	_wCharm->fill();
      }
      bool lightTagged = false;
      if(!charmTagged) {
	for(const Particle & p : cfs.particles()) {
	  if(p.p3().mod()>9.43*GeV) {
	    pTag=p;
	    lightTagged=true;
	    _wLight->fill();
	    break;
	  }
	}
      }
      // sign of hemispheres if tagged
      double sign=1.;
      if(charmTagged || lightTagged) {
	if(dot(axis,pTag.p3())<0.) sign=-1.;
      }
      // now loop over the kaons
      for(const Particle & p : ufs.particles(Cuts::pid==130 || Cuts::pid==310)) {
         double xE = p.E()/meanBeamMom;
	 const double energy = p.E();
	 const double momT = dot(axis, p.p3());
	 _h_X->fill(xE);
	 double rap = 0.5 * std::log((energy + momT) / (energy - momT));
	 _h_rap_all->fill(fabs(rap));
	 rap *=sign;
	 if(charmTagged)
	   _h_rap_charm->fill(rap);
	 else if(lightTagged)
	   _h_rap_light->fill(rap);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_X        , crossSection()*sqr(sqrtS())/nanobarn/sumOfWeights());
      scale(_h_rap_all  , 1./sumOfWeights());
      scale(_h_rap_light, 1./ *_wLight);
      scale(_h_rap_charm, 1./ *_wCharm);
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_X, _h_rap_all,_h_rap_light,_h_rap_charm;
    CounterPtr _wLight,_wCharm;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(HRS_1990_I280958);


}