rivet is hosted by Hepforge, IPPP Durham

Rivet analyses reference

BABAR_2018_I1667191

Mass and angular distributions in the radiative decays $\Upsilon(1S)\to\pi^+\pi^-$ and $K^+K^-$
Experiment: BABAR (PEP-II)
Inspire ID: 1667191
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.D 97 (2018) 11, 112006
Beams: * *
Beam energies: ANY
Run details:
  • Upsilon(1S) produced in the decays Upsilon(2,3S)-> Upsilon(1S) pi+ pi- (need for photon angle dist)

Mass and angular distributions in the radiative decays $\Upsilon(1S)\to\pi^+\pi^-$ and $K^+K^-$

Source code: BABAR_2018_I1667191.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
// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/DecayedParticles.hh"

namespace Rivet {


  /// @brief Upsilon(1S) -> gamma pi+pi- K+K-
  class BABAR_2018_I1667191 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2018_I1667191);


    /// @name Analysis methods
    /// @{

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==200553 or
						Cuts::abspid==100553);
      declare(ufs, "UFS");
      DecayedParticles UPS(ufs);
      UPS.addStable( 553);
      declare(UPS, "UPS");
      // histograms
      for(unsigned int ix=0;ix<2;++ix)
	book(_h_mass[ix],1+ix,1,1);
      book(_h_pi,3,1,1);
      for(unsigned int ix=0;ix<3;++ix)
	for(unsigned int iy=0;iy<2;++iy)
	  book(_h_angle[ix][iy],4+ix,1,1+iy);
    }


   /// Recursively walk the decay tree to find decay products of @a p
    void findDecayProducts(Particle mother, Particles& gamma,
			   Particles & pip, Particles & pim,
			   Particles & Kp , Particles & Km,unsigned int & nstable) {
      for(const Particle & p: mother.children()) {
	if     (p.pid()== 211) pip.push_back(p);
	else if(p.pid()==-211) pim.push_back(p);
	else if(p.pid()== 321) Kp .push_back(p);
	else if(p.pid()==-321) Km .push_back(p);
	else if(p.pid()==22) gamma.push_back(p);
	else if(p.children().empty())
	  nstable+=1;
	else {
	  findDecayProducts(p, gamma,pip,pim,Kp,Km,nstable);
	  
	}
      }
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId,unsigned int> & mode   = { { 553,1},{ 211,1}, {-211,1}};
      DecayedParticles UPS = apply<DecayedParticles>(event, "UPS");
      // loop over particles
      for(unsigned int ix=0;ix<UPS.decaying().size();++ix) {
	// check pi+pi- upslion(1S) decay mode
      	if (!UPS.modeMatches(ix,3,mode)) continue;
	const Particle  & ups1 = UPS.decayProducts()[ix].at( 553)[0];
	const Particle  & pips = UPS.decayProducts()[ix].at( 211)[0];
	const Particle  & pims = UPS.decayProducts()[ix].at(-211)[0];
	// boost to rest frame
	LorentzTransform boost;
	if (UPS.decaying()[ix].p3().mod() > 1*MeV)
	  boost = LorentzTransform::mkFrameTransformFromBeta(UPS.decaying()[ix].momentum().betaVec());
	FourMomentum ppipi = boost.transform(pips.momentum()+pims.momentum());
	Vector3 axis1 = ppipi.p3().unit();
	LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(ppipi);
	FourMomentum ppi = boost1.transform(boost.transform(pips.momentum()));
	_h_pi->fill(abs(ppi.p3().unit().dot(axis1)));
	unsigned int nstable=0;
	Particles gamma,pip,pim,Kp,Km;
	findDecayProducts(ups1, gamma,pip,pim,Kp,Km,nstable);
	if(gamma.size()!=1 || nstable!=0) continue;
	// gamma pi+pi-
	if(Kp.empty()&&Km.empty()&&pip.size()==1&&pim.size()==1) {
	  ppipi = pip[0].momentum()+pim[0].momentum();
	  double mpipi = ppipi.mass();
	  _h_mass[0]->fill(mpipi);
	  axis1 *=-1;
	  LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(boost.transform(ups1.momentum()).betaVec());
	  FourMomentum pgamma = boost2.transform(boost.transform(gamma[0].momentum()));
	  Vector3 axis2 = pgamma.p3().unit();
	  double cGamma = axis2.dot(axis1);
	  ppipi = boost2.transform(boost1.transform(ppipi));
	  LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
	  Vector3 axis3 = boost3.transform(boost2.transform(boost1.transform(pip[0].momentum()))).p3().unit();
	  double cH = axis3.dot(axis2);
	  int iloc=-1;
	  if(mpipi>0.6&&mpipi<1.)          iloc=0;
	  else if(mpipi>1.092&&mpipi<1.46) iloc=1;
	  if(iloc>=0) {
	    _h_angle[iloc][0]->fill(cGamma);
	    _h_angle[iloc][1]->fill(cH);
	  }
	}
	// gamma K+K-
	else if (pip.empty()&&pim.empty()&&Kp.size()==1&&Km.size()==1) {
	  FourMomentum pKK = Kp[0].momentum()+Km[0].momentum(); 
	  double mKK = pKK.mass();
	  _h_mass[1]->fill(mKK);
	  axis1 *=-1;
	  LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(boost.transform(ups1.momentum()).betaVec());
	  FourMomentum pgamma = boost2.transform(boost.transform(gamma[0].momentum()));
	  Vector3 axis2 = pgamma.p3().unit();
	  double cGamma = axis2.dot(axis1);
	  pKK = boost2.transform(boost1.transform(pKK));
	  LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pKK.betaVec());
	  Vector3 axis3 = boost3.transform(boost2.transform(boost1.transform(Kp[0].momentum()))).p3().unit();
	  double cH = axis3.dot(axis2);
	  if(mKK>1.424 && mKK<1.62) {
	    _h_angle[2][0]->fill(cGamma);
	    _h_angle[2][1]->fill(cH);
	  }
	}
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for(unsigned int ix=0;ix<2;++ix)
	normalize(_h_mass[ix],1.,false);
      normalize(_h_pi,1.,false);
      for(unsigned int ix=0;ix<3;++ix)
	for(unsigned int iy=0;iy<2;++iy)
	  normalize(_h_angle[ix][iy],1.,false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[2];
    Histo1DPtr _h_pi;
    Histo1DPtr _h_angle[3][2];
    /// @}

  };


  RIVET_DECLARE_PLUGIN(BABAR_2018_I1667191);

}