Rivet Analyses Reference

AMY_1990_I283337

Event shapes in $e^+e^-$ collisions at 55.2 GeV
Experiment: AMY (Tristan)
Inspire ID: 283337
Status: VALIDATED
Authors:
  • Your Name
References:
  • Phys.Rev. D41 (1990) 2675, 1990
Beams: e- e+
Beam energies: (27.6, 27.6) GeV
Run details:
  • e+e- to hadrons

Measurement of a wide range of event shapes by the AMY experiment at Tristan with an average centre-of-mass energy of $55.2$ GeV.

Source code: AMY_1990_I283337.cc
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/Sphericity.hh"
#include "Rivet/Projections/Thrust.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/Hemispheres.hh"

namespace Rivet {

  /// @brief Event shapes at 55.2
  class AMY_1990_I283337 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(AMY_1990_I283337);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {
      declare(Beam(), "Beams");
      const FinalState fs;
      declare(fs, "FS");
      const Sphericity sphere(fs);
      declare(sphere, "Sphericity");
      const Thrust thrust(fs);
      declare(thrust, "Thrust");
      declare(Hemispheres(sphere), "Hemispheres");
      // histograms
      book(_histRapidityT , 1, 1, 1);
      book(_histScaledMom , 2, 1, 1);
      book(_histPl        , 3, 1, 1);
      book(_histPt        , 4, 1, 1);
      book(_histPt2       , 5, 1, 1);
      book(_histPtIn      , 6, 1, 1);
      book(_histPtOut     , 7, 1, 1);
      book(_histMeanPtIn2 , 8, 1, 1);
      book(_histMeanPtOut2, 9, 1, 1);
      book(_histNtheta    ,10, 1, 1);
      book(_histEtheta    ,11, 1, 1);
      book(_histThrust    ,12, 1, 1);
      book(_histMajor     ,13, 1, 1);
      book(_histMinor     ,14, 1, 1);
      book(_histOblateness,15, 1, 1);
      book(_histSphericity,16, 1, 1);
      book(_histAplanarity,17, 1, 1);
      book(_histQx        ,18, 1, 1);
      book(_histQ21       ,19, 1, 1);
      book(_histRhoLight  ,20, 1, 1);
      book(_histRhoHeavy  ,21, 1, 1);
      book(_histRhoDiff   ,22, 1, 1);
      book(_wSum,"TMP/wSum");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // First, veto on leptonic events by requiring at least 4 charged FS particles
      const FinalState& fs = apply<FinalState>(event, "FS");
      const size_t numParticles = fs.particles().size();
      // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
      if (numParticles < 2) {
        MSG_DEBUG("Failed leptonic event cut");
        vetoEvent;
      }
      MSG_DEBUG("Passed leptonic event cut");
      _wSum->fill();

      // 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);

      // Thrusts
      MSG_DEBUG("Calculating thrust");
      const Thrust& thrust = apply<Thrust>(event, "Thrust");
      _histThrust    ->fill(thrust.thrust()     );
      _histMajor     ->fill(thrust.thrustMajor());
      _histMinor     ->fill(thrust.thrustMinor());
      _histOblateness->fill(thrust.oblateness() );
      // Sphericities
      MSG_DEBUG("Calculating sphericity");
      const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");
      _histSphericity->fill(sphericity.sphericity());
      _histAplanarity->fill(sphericity.aplanarity());
      _histQx        ->fill(sqrt(1./3.)*(sphericity.lambda1()-sphericity.lambda2()));
      _histQ21       ->fill(sphericity.lambda2()-sphericity.lambda3());
      // Hemispheres
      MSG_DEBUG("Calculating hemisphere variables");
      const Hemispheres& hemi = apply<Hemispheres>(event, "Hemispheres");
      _histRhoHeavy->fill(hemi.scaledM2high());
      _histRhoLight->fill(hemi.scaledM2low() );
      _histRhoDiff ->fill(hemi.scaledM2diff());
      // single particle distributions
      double pTIn2(0.),pTOut2(0.);
      unsigned int nCharged(0);
      for (const Particle& p : fs.particles()) {
        // Get momentum and energy of each particle.
        const Vector3 mom3 = p.p3();
        const double energy = p.E();
        const double mom = mom3.mod();
        const double scaledMom = mom/meanBeamMom;
        const double momT = dot(thrust.thrustAxis(), mom3);
        const double momS = dot(sphericity.sphericityAxis(), mom3);
        const double pTinS = dot(mom3, sphericity.sphericityMajorAxis());
        const double pToutS = dot(mom3, sphericity.sphericityMinorAxis());
        const double pT = sqrt(pow(pTinS, 2) + pow(pToutS, 2));

        const double rapidityT = 0.5 * std::log((energy + momT) / (energy - momT));
        double angle = sphericity.sphericityAxis().angle(p.p3())/M_PI*180.;
        if(angle>90.) angle=180.-angle;
        if(PID::isCharged(p.pid())) {
          _histScaledMom->fill(scaledMom);
          _histRapidityT->fill(fabs(rapidityT));
          _histPl       ->fill(fabs(momS)     );
          _histPt       ->fill(pT             );
          _histPt2      ->fill(sqr(pT)        );
          _histPtIn     ->fill(fabs(pTinS)    );
          _histPtOut    ->fill(fabs(pToutS)   );
          pTIn2  += sqr(pTinS);
          pTOut2 += sqr(pToutS);
          _histNtheta->fill(angle);
          ++nCharged;
        }
        _histEtheta->fill(angle,energy); 
      }
      if (nCharged) {
        _histMeanPtIn2 ->fill( pTIn2/nCharged);
        _histMeanPtOut2->fill(pTOut2/nCharged);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // histograms
      scale(_histRapidityT , 1./ *_wSum);
      scale(_histScaledMom , 1./ *_wSum);
      scale(_histPl        , 1./ *_wSum);
      scale(_histPt        , 1./ *_wSum);
      scale(_histPt2       , 1./ *_wSum);
      scale(_histPtIn      , 1./ *_wSum);
      scale(_histPtOut     , 1./ *_wSum);
      scale(_histMeanPtIn2 , 1./ *_wSum);
      scale(_histMeanPtOut2, 1./ *_wSum);
      scale(_histNtheta    , 1./ *_wSum);
      scale(_histEtheta    , 1./ *_wSum);
      scale(_histThrust    , 1./ *_wSum);
      scale(_histMajor     , 1./ *_wSum);
      scale(_histMinor     , 1./ *_wSum);
      scale(_histOblateness, 1./ *_wSum);
      scale(_histSphericity, 1./ *_wSum);
      scale(_histAplanarity, 1./ *_wSum);
      scale(_histQx        , 1./ *_wSum);
      scale(_histQ21       , 1./ *_wSum);
      scale(_histRhoLight  , 1./ *_wSum);
      scale(_histRhoHeavy  , 1./ *_wSum);
      scale(_histRhoDiff   , 1./ *_wSum);
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _histRapidityT, _histScaledMom, _histPl, _histPt, _histPt2, _histPtIn, _histPtOut,
      _histMeanPtIn2, _histMeanPtOut2, _histNtheta, _histEtheta, _histThrust, _histMajor, _histMinor,
      _histOblateness, _histSphericity, _histAplanarity, _histQx, _histQ21, _histRhoLight,
      _histRhoHeavy, _histRhoDiff;
    CounterPtr _wSum;
    //@}


  };


  // The hook for the plugin system
  RIVET_DECLARE_PLUGIN(AMY_1990_I283337);


}