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BESII_2007_I763951

Mass distributions in $\psi(2S)\to\gamma\pi^+\pi^-$ and $\psi(2S)\to\gamma K^+K^-$
Experiment: BESII (BEPC)
Inspire ID: 763951
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References: Beams: * *
Beam energies: ANY
Run details:
  • Any process producing psi(2S), originally e+e-

Measurement of the pion pair mass distribution in $\psi(2S)\to\gamma\pi^+\pi^-$ and $\psi(2S)\to\gamma K^+K^-$. The data were read from the plots in the paper and the backgrounds given subtracted.

Source code: BESII_2007_I763951.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  psi(2S) -> gamma pi+pi- / K+K-
10  class BESII_2007_I763951 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2007_I763951);
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==100443);
24      declare(ufs, "UFS");
25      DecayedParticles PSI(ufs);
26      PSI.addStable(PID::ETA);
27      PSI.addStable(PID::PI0);
28      declare(PSI, "PSI");
29      // histos
30      for (unsigned int ix=0;ix<2;++ix) {
31        book(_h[ix],1+ix,1,1);
32      }
33    }
34
35
36    /// Perform the per-event analysis
37    void analyze(const Event& event) {
38      // find the J/psi decays
39      DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
40      // loop over particles
41      for (unsigned int ix=0; ix<PSI.decaying().size(); ++ix) {
42        unsigned int imode=0;
43        if (PSI.modeMatches(ix,3,mode1))      imode=0;
44        else if (PSI.modeMatches(ix,3,mode2)) imode=1;
45        else continue;
46        const Particle& gam = PSI.decayProducts()[0].at( 22)[0];
47        _h[imode]->fill((PSI.decaying()[ix].mom()-gam.mom()).mass());
48      }
49    }
50
51
52    /// Normalise histograms etc., after the run
53    void finalize() {
54      normalize(_h, 1.0, false);
55    }
56
57    /// @}
58
59
60    /// @name Histograms
61    /// @{
62    Histo1DPtr _h[2];
63    const map<PdgId,unsigned int> mode1 = { { 211,1}, {-211,1}, { 22,1}};
64    const map<PdgId,unsigned int> mode2 = { { 321,1}, {-321,1}, { 22,1}};
65    /// @}
66
67
68  };
69
70
71  RIVET_DECLARE_PLUGIN(BESII_2007_I763951);
72
73}