Rivet Analyses Reference

  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

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Upsilon(2S) -> Upsilon(1S) pi+pi-
  class CLEOII_1998_I467642 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1998_I467642);


    /// @name Analysis methods
    //@{

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

      // Initialise and register projections
      declare(UnstableParticles(),"UFS");
      book(_h_charged_ex   ,1,1,1);
      book(_h_charged_inc  ,2,1,1);
      book(_h_neutral_ex   ,3,1,1);
      book( _h_lept_ctheta ,4,1,1);
      book(_h_lept_phi     ,4,1,2);
      book(_h_piStar_ctheta,5,1,1);
      book(_h_piStar_phi   ,5,1,2);
      book(_h_pi_ctheta    ,6,1,1);
      book(_h_pi_phi       ,6,1,2);

    }

    void findDecayProducts(const Particle & mother,
			   unsigned int & nstable,
			   Particles& pip, Particles& pim,
			   Particles& pi0, Particles & onium) {
      for(const Particle & p : mother.children()) {
        int id = p.pid();
      	if ( id == PID::PIMINUS) {
	  pim.push_back(p);
	  ++nstable;
	}
       	else if (id == PID::PIPLUS) {
       	  pip.push_back(p);
       	  ++nstable;
       	}
       	else if (id == PID::PI0) {
       	  pi0.push_back(p);
       	  ++nstable;
       	}
	else if (abs(id)%1000==443 || abs(id)%1000==553) {
	  onium.push_back(p);
	  ++nstable;
	}
	else if ( !p.children().empty() ) {
	  findDecayProducts(p,nstable,pip,pim,pi0,onium);
	}
	else
	  ++nstable;
      }
    }

    void findLeptons(const Particle & mother,
		     unsigned int & nstable,
		     Particles& lp, Particles& lm) {
      for(const Particle & p : mother.children()) {
        int id = p.pid();
      	if ( id == 11 || id == 13 ) {
	  lm.push_back(p);
	  ++nstable;
	}
       	else if (id == -11 || id==-13) {
       	  lp.push_back(p);
       	  ++nstable;
       	}
	else if ( !p.children().empty() ) {
	  findLeptons(p,nstable,lp,lm);
	}
	else
	  ++nstable;
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // loop over unstable particles
      for(const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==100553)) {
	unsigned int nstable(0);
	Particles pip, pim, pi0, onium;
	findDecayProducts(ups,nstable,pip,pim,pi0,onium);
	// check for onium
	if(onium.size() !=1 || onium[0].pid()!=553 || nstable !=3) continue;
	//pi+pi-
	if( pip.size()==1 && pim.size() ==1) {
	  FourMomentum q = pip[0].momentum()+pim[0].momentum();
	  _h_charged_ex->fill(q.mass()/GeV);
	  _h_charged_inc->fill(q.mass()/GeV);
	  // leptons from Upsilon(1S) decay
	  nstable = 0;
	  Particles lp, lm;
	  findLeptons(onium[0],nstable,lp,lm);
	  if(nstable==2&&lp.size()==1&&lm.size()==1) {
	    _h_lept_ctheta->fill(cos(lp[0].momentum().polarAngle()));
	    _h_lept_phi   ->fill(lp[0].momentum().azimuthalAngle());
	  }
	  // pions in rest frame
	  LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(q.betaVec());
	  FourMomentum ppi = boost.transform(pip[0].momentum());
	  Vector3 axis1 = q.p3().unit();
	  Vector3 axis2 = Vector3(0.,0.,1.).cross(axis1).unit();
	  Vector3 axis3 = axis1.cross(axis2).unit();
	  _h_piStar_ctheta->fill(axis1.dot(ppi.p3().unit()));
	  double phi = atan2(axis3.dot(ppi.p3().unit()),axis2.dot(ppi.p3().unit()));
	  if(phi<0.) phi+=2.*M_PI;
	  _h_piStar_phi->fill(phi);
	  // pions in lab frame
	  _h_pi_ctheta->fill(cos(q.polarAngle()));
	  _h_pi_phi   ->fill(q.azimuthalAngle());
	}
	// 2pi0
	else if (pi0.size()==2) {
	  FourMomentum q = pi0[0].momentum()+pi0[1].momentum();
	  _h_neutral_ex->fill(q.mass()/GeV);
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_charged_ex);
      normalize(_h_charged_inc);
      normalize(_h_neutral_ex);
      normalize( _h_lept_ctheta);
      normalize(_h_lept_phi);
      normalize(_h_piStar_ctheta);
      normalize(_h_piStar_phi);
      normalize(_h_pi_ctheta);
      normalize(_h_pi_phi);
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_charged_ex,_h_charged_inc,_h_neutral_ex;
    Histo1DPtr _h_lept_ctheta,_h_lept_phi,_h_piStar_ctheta,_h_piStar_phi,_h_pi_ctheta,_h_pi_phi;
    //@}


  };


  RIVET_DECLARE_PLUGIN(CLEOII_1998_I467642);

}