Rivet analyses referenceBESIII_2017_I1490896$\chi_{c1}\to \eta\pi^+\pi^-$Experiment: BESIII (BEPC) Inspire ID: 1490896 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the mass distributions in the decays $\chi_{c1}\to \eta\pi^+\pi^-$. The data were read from the plots in the paper and may not be corrected for efficiency. Source code: BESIII_2017_I1490896.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 chi_c1 -> eta pi+pi-
10 class BESIII_2017_I1490896 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1490896);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 UnstableParticles ufs = UnstableParticles(Cuts::pid==20443);
23 declare(ufs, "UFS");
24 DecayedParticles chi(ufs);
25 chi.addStable( PID::PI0);
26 chi.addStable( PID::K0S);
27 chi.addStable( PID::ETA);
28 declare(chi, "chi");
29 for(unsigned int ix=0;ix<2;++ix)
30 book(_h[ix],1,1,ix+1);
31 book(_dalitz,"dalitz",50,0.,12.,50,0., 9.);
32 }
33
34
35 /// Perform the per-event analysis
36 void analyze(const Event& event) {
37 static const map<PdgId,unsigned int> & mode1 = { { 221,1}, { 211,1}, {-211,1} };
38 DecayedParticles chi = apply<DecayedParticles>(event, "chi");
39 // loop over particles
40 for(unsigned int ix=0;ix<chi.decaying().size();++ix) {
41 if(chi.modeMatches(ix,3,mode1)) {
42 const Particle & eta = chi.decayProducts()[ix].at( 221)[0];
43 const Particle & pim = chi.decayProducts()[ix].at(-211)[0];
44 const Particle & pip = chi.decayProducts()[ix].at( 211)[0];
45 double m1 = (pip.momentum()+pim.momentum()).mass2();
46 double m2 = (eta.momentum()+pip.momentum()).mass2();
47 double m3 = (eta.momentum()+pim.momentum()).mass2();
48 _dalitz->fill(m2,m1);
49 _h[1]->fill(sqrt(m1));
50 _h[0]->fill(sqrt(m2));
51 _h[0]->fill(sqrt(m3));
52 }
53 }
54 }
55
56
57 /// Normalise histograms etc., after the run
58 void finalize() {
59 normalize(_dalitz);
60 for(unsigned int iy=0;iy<2;++iy)
61 normalize(_h[iy]);
62 }
63 /// @}
64
65 /// @name Histograms
66 /// @{
67 Histo1DPtr _h[2];
68 Histo2DPtr _dalitz;
69 /// @}
70
71 };
72
73
74 RIVET_DECLARE_PLUGIN(BESIII_2017_I1490896);
75
76}
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