Rivet analyses referenceBES_1999_I507639Hadronic mass distribution in $J/\psi\to\gamma \pi^+\pi^-\pi^+\pi^-$Experiment: BES (BEPC) Inspire ID: 507639 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Hadronic mass distribution in $J/\psi\to\gamma \pi^+\pi^-\pi^+\pi^-$. Only the $\pi^+\pi^-\pi^+\pi^-$ mass distribution isa implemented as the background is not given for the other distributions. The data were read from figure 4d and the background given subtracted. Source code: BES_1999_I507639.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/DecayedParticles.hh"
5
6namespace Rivet {
7
8
9 /// @brief J/psi -> gamma 2pi+ 2pi-
10 class BES_1999_I507639 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BES_1999_I507639);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // Initialise and register projections
23 UnstableParticles ufs = UnstableParticles(Cuts::abspid==443);
24 declare(ufs, "UFS");
25 DecayedParticles PSI(ufs);
26 PSI.addStable(PID::K0S);
27 PSI.addStable(PID::PI0);
28 declare(PSI, "PSI");
29 // histos
30 book(_h,1,1,1);
31 }
32
33
34 /// Perform the per-event analysis
35 void analyze(const Event& event) {
36 // find the J/psi decays
37 DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
38 // loop over particles
39 for (unsigned int ix=0; ix<PSI.decaying().size(); ++ix) {
40 if (!PSI.modeMatches(ix,5,mode)) continue;
41 const Particles& pip = PSI.decayProducts()[0].at( 211);
42 const Particles& pim = PSI.decayProducts()[0].at(-211);
43 FourMomentum ptotal;
44 for (unsigned int iy=0; iy<2; ++iy) {
45 ptotal+=pip[ix].momentum()+pim[ix].momentum();
46 }
47 _h->fill(ptotal.mass());
48 }
49 }
50
51
52 /// Normalise histograms etc., after the run
53 void finalize() {
54 normalize(_h,1.,false);
55 }
56
57 /// @}
58
59
60 /// @name Histograms
61 /// @{
62 Histo1DPtr _h;
63 const map<PdgId,unsigned int> mode = { { 211,2}, {-211,2}, { 22,1}};
64 /// @}
65
66
67 };
68
69
70 RIVET_DECLARE_PLUGIN(BES_1999_I507639);
71
72}
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