Rivet analyses referenceMARKII_1979_I144382$\pi^+\pi^-$ spectrum in $\psi(2S)\to\pi^+\pi^-J/\psi$Experiment: MARKII (SPEAR) Inspire ID: 144382 Status: VALIDATED Authors:
Beams: * * Beam energies: ANY
Measurement of the mass spectrum for $\pi^+\pi^-$ in $\psi(2S)\to\pi^+\pi^-J/\psi$ decays by the MARK-II experiment. Source code: MARKII_1979_I144382.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief psi(2S) -> J/psi pi+pi-
9 class MARKII_1979_I144382 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(MARKII_1979_I144382);
14
15
16 /// @name Analysis methods
17 ///@{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21
22 // Initialise and register projections
23 declare(UnstableParticles(),"UFS");
24 book(_hist, 1, 1, 1);
25
26 }
27
28
29 void findDecayProducts(const Particle & mother,
30 unsigned int & nstable,
31 Particles& pip, Particles& pim,
32 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==443) {
44 onium.push_back(p);
45 ++nstable;
46 }
47 else if ( !p.children().empty() ) {
48 findDecayProducts(p,nstable,pip,pim,onium);
49 }
50 else
51 ++nstable;
52 }
53 }
54
55 /// Perform the per-event analysis
56 void analyze(const Event& event) {
57 // loop over unstable particles
58 for(const Particle& ups : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid==100443)) {
59 unsigned int nstable(0);
60 Particles pip, pim, onium;
61 findDecayProducts(ups,nstable,pip,pim,onium);
62 // check for onium
63 if(onium.size() !=1 || nstable !=3 || pip.size()!=1 || pim.size() !=1 ) continue;
64 FourMomentum q = pip[0].momentum()+pim[0].momentum();
65 _hist->fill(q.mass2());
66 }
67 }
68
69
70 /// Normalise histograms etc., after the run
71 void finalize() {
72 normalize(_hist);
73 }
74
75 ///@}
76
77
78 /// @name Histograms
79 ///@{
80 Histo1DPtr _hist;
81 ///@}
82
83
84 };
85
86
87 RIVET_DECLARE_PLUGIN(MARKII_1979_I144382);
88
89}
|