Rivet analyses referenceBELLE_2017_I1610301$\Upsilon(2,3,4S)\to\Upsilon(1S)\pi^+\pi^-$ and $\Upsilon(4S)\to\Upsilon(2S)\pi^+\pi^-$Experiment: BELLE (KEKB) Inspire ID: 1610301 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the $\pi^+\pi^-$ mass Spectrum and pion helicity angle in $\Upsilon(2,3,4S)\to\Upsilon(1S)\pi^+\pi^-$ and $\Upsilon(4S)\to\Upsilon(2S)\pi^+\pi^-$ decays by the BELLE collaboration. Source code: BELLE_2017_I1610301.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief Upsilon -> Upsilon pi+pi-
9 class BELLE_2017_I1610301 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2017_I1610301);
14
15
16 /// @name Analysis methods
17 ///@{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21 // Initialise and register projections
22 declare(UnstableParticles(),"UFS");
23 for(unsigned int ix=0;ix<4;++ix) {
24 book(_h_mpipi [ix],1,1,ix+1);
25 book(_h_ctheta[ix],2,1,ix+1);
26 }
27 }
28
29 void findDecayProducts(const Particle & mother,
30 unsigned int & nstable,
31 Particles& pip, Particles& pim,
32 Particles& pi0, Particles & onium) {
33 for(const Particle & p : mother.children()) {
34 int id = p.pid();
35 if ( id == PID::PIMINUS) {
36 pim.push_back(p);
37 ++nstable;
38 }
39 else if (id == PID::PIPLUS) {
40 pip.push_back(p);
41 ++nstable;
42 }
43 else if (id == PID::PI0) {
44 pi0.push_back(p);
45 ++nstable;
46 }
47 else if (abs(id)%1000==443 || abs(id)%1000==553) {
48 onium.push_back(p);
49 ++nstable;
50 }
51 else if ( !p.children().empty() ) {
52 findDecayProducts(p,nstable,pip,pim,pi0,onium);
53 }
54 else
55 ++nstable;
56 }
57 }
58
59 /// Perform the per-event analysis
60 void analyze(const Event& event) {
61 for(const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==100553 or
62 Cuts::pid==200553 or
63 Cuts::pid==300553)) {
64 unsigned int nstable(0);
65 Particles pip, pim, pi0, onium;
66 findDecayProducts(ups,nstable,pip,pim,pi0,onium);
67 // pions and no of products
68 if(pip.size()!=1 || pim.size() !=1 || nstable !=3) continue;
69 // check for onium
70 if(onium.size() !=1) continue;
71 if(!(onium[0].pid()==553 || (ups.pid()==300553 && onium[0].pid()==100553))) continue;
72 FourMomentum q = pip[0].momentum()+pim[0].momentum();
73 // boost particles to upsilon rest frame
74 LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
75 FourMomentum ppi = boost1.transform(pip[0].momentum());
76 FourMomentum pUps = boost1.transform(onium[0].momentum());
77 q = boost1.transform(q);
78 LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(q.betaVec());
79 ppi = boost2.transform(ppi);
80 pUps = boost2.transform(pUps);
81 double ctheta = ppi.p3().unit().dot(pUps.p3().unit());
82 if(ups.pid()==100553) {
83 _h_mpipi[0]->fill(q.mass());
84 _h_ctheta[0]->fill(ctheta);
85 }
86 else if(ups.pid()==200553) {
87 _h_mpipi[1]->fill(q.mass());
88 _h_ctheta[1]->fill(ctheta);
89 }
90 else if(ups.pid()==300553) {
91 if(onium[0].pid()==553) {
92 _h_mpipi[2]->fill(q.mass());
93 _h_ctheta[2]->fill(ctheta);
94 }
95 else {
96 _h_mpipi[3]->fill(q.mass());
97 _h_ctheta[3]->fill(ctheta);
98 }
99 }
100 }
101 }
102
103
104 /// Normalise histograms etc., after the run
105 void finalize() {
106 for(unsigned int ix=0;ix<4;++ix) {
107 normalize(_h_mpipi [ix]);
108 normalize(_h_ctheta[ix]);
109 }
110 }
111
112 ///@}
113
114
115 /// @name Histograms
116 ///@{
117 Histo1DPtr _h_mpipi [4];
118 Histo1DPtr _h_ctheta[4];
119 ///@}
120
121
122 };
123
124
125 RIVET_DECLARE_PLUGIN(BELLE_2017_I1610301);
126
127}
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