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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 charged 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
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/Beam.hh"
  4#include "Rivet/Projections/Thrust.hh"
  5#include "Rivet/Projections/ChargedFinalState.hh"
  6#include "Rivet/Projections/UnstableParticles.hh"
  7
  8namespace Rivet {
  9
 10
 11  /// @brief Add a short analysis description here
 12  class HRS_1990_I280958 : public Analysis {
 13  public:
 14
 15    /// Constructor
 16    RIVET_DEFAULT_ANALYSIS_CTOR(HRS_1990_I280958);
 17
 18
 19    /// @name Analysis methods
 20    //@{
 21
 22    /// Book histograms and initialise projections before the run
 23    void init() {
 24
 25      // Initialise and register projections
 26      declare(Beam(), "Beams");
 27      declare(UnstableParticles(), "UFS");
 28      const ChargedFinalState cfs;
 29      declare(cfs, "CFS");
 30      declare(Thrust(cfs), "Thrust");
 31
 32      // Book histograms
 33      book(_h_X        , 3, 1, 1);
 34      book(_h_rap_all  , 4, 1, 1);
 35      book(_h_rap_light, 6, 1, 1);
 36      book(_h_rap_charm, 5, 1, 1);
 37      book(_wLight,"TMP/wLight");
 38      book(_wCharm,"TMP/wCharm");
 39    }
 40
 41
 42    /// Perform the per-event analysis
 43    void analyze(const Event& event) {
 44      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
 45      int nch = cfs.particles().size();
 46      if(nch<5) vetoEvent;
 47      // Get beams and average beam momentum
 48      const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
 49      const double meanBeamMom = ( beams.first.p3().mod() +
 50                                   beams.second.p3().mod() ) / 2.0;
 51      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
 52      // get the thrust axes
 53      const Thrust& thrust = apply<Thrust>(event, "Thrust");
 54      const Vector3 & axis = thrust.thrustAxis();
 55      // unstable particles
 56      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
 57      Particle pTag;
 58      // get the tags
 59      Particles Dstar = ufs.particles(Cuts::abspid==413);
 60      bool charmTagged = !Dstar.empty();
 61      if(charmTagged) {
 62	pTag = Dstar[0];
 63	for(const Particle & p : Dstar) {
 64	  if(p.E()>pTag.E()) pTag=p;
 65	}
 66	_wCharm->fill();
 67      }
 68      bool lightTagged = false;
 69      if(!charmTagged) {
 70	for(const Particle & p : cfs.particles()) {
 71	  if(p.p3().mod()>9.43*GeV) {
 72	    pTag=p;
 73	    lightTagged=true;
 74	    _wLight->fill();
 75	    break;
 76	  }
 77	}
 78      }
 79      // sign of hemispheres if tagged
 80      double sign=1.;
 81      if(charmTagged || lightTagged) {
 82	if(dot(axis,pTag.p3())<0.) sign=-1.;
 83      }
 84      // now loop over the kaons
 85      for(const Particle & p : ufs.particles(Cuts::pid==130 || Cuts::pid==310)) {
 86         double xE = p.E()/meanBeamMom;
 87	 const double energy = p.E();
 88	 const double momT = dot(axis, p.p3());
 89	 _h_X->fill(xE);
 90	 double rap = 0.5 * std::log((energy + momT) / (energy - momT));
 91	 _h_rap_all->fill(fabs(rap));
 92	 rap *=sign;
 93	 if(charmTagged)
 94	   _h_rap_charm->fill(rap);
 95	 else if(lightTagged)
 96	   _h_rap_light->fill(rap);
 97      }
 98    }
 99
100
101    /// Normalise histograms etc., after the run
102    void finalize() {
103      scale(_h_X        , crossSection()*sqr(sqrtS())/nanobarn/sumOfWeights());
104      scale(_h_rap_all  , 1./sumOfWeights());
105      scale(_h_rap_light, 1./ *_wLight);
106      scale(_h_rap_charm, 1./ *_wCharm);
107    }
108
109    //@}
110
111
112    /// @name Histograms
113    //@{
114    Histo1DPtr _h_X, _h_rap_all,_h_rap_light,_h_rap_charm;
115    CounterPtr _wLight,_wCharm;
116    //@}
117
118
119  };
120
121
122  // The hook for the plugin system
123  RIVET_DECLARE_PLUGIN(HRS_1990_I280958);
124
125
126}