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BESIII_2022_I2615968

Dalitz plot analysis of $D^0\to K^0_{S,L}\pi^+\pi^-$
Experiment: BESIII (BEPC)
Inspire ID: 2615968
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References: Beams: * *
Beam energies: ANY
Run details:
  • Any process producing D0 mesons

Measurement of Kinematic distributions in the decay $D^0\to K^0_S\pi^+\pi^-$ by BESIII. The data were read from the plots in the paper and resolution/acceptance effects may not have been unfolded.

Source code: BESIII_2022_I2615968.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 D0 -> KS0, KL0 pi+ pi-
10  class BESIII_2022_I2615968 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2022_I2615968);
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==421);
24      declare(ufs, "UFS");
25      DecayedParticles D0(ufs);
26      D0.addStable(PID::PI0);
27      D0.addStable(PID::K0S);
28      D0.addStable(PID::ETA);
29      D0.addStable(PID::ETAPRIME);
30      declare(D0, "D0");
31      // Histograms
32      for(unsigned int ix=0;ix<2;++ix)
33	for(unsigned int iy=0;iy<3;++iy)
34	  book(_h[ix][iy],1+ix,1,1+iy);
35    }
36
37
38    /// Perform the per-event analysis
39    void analyze(const Event& event) {
40      // // define the decay mode
41      static const map<PdgId,unsigned int> & mode1 = { { 310,1}, { 211,1},{-211,1}};
42      static const map<PdgId,unsigned int> & mode2 = { { 130,1}, { 211,1},{-211,1}};
43      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
44      // loop over particles
45      for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
46       	int sign = D0.decaying()[ix].pid()/421;
47	int imode = 0;
48       	// KS0 pi+pi-
49       	if      (D0.modeMatches(ix,3,mode1) ) imode=0;
50	else if (D0.modeMatches(ix,3,mode2) ) imode=1;
51	else continue;
52       	const Particle & pip= D0.decayProducts()[ix].at( sign*211)[0];
53       	const Particle & pim= D0.decayProducts()[ix].at(-sign*211)[0];
54       	const Particle & K0 = D0.decayProducts()[ix].at( imode==0 ? 310 : 130)[0];
55      	double mminus = (pim.momentum()+K0.momentum() ).mass2();
56      	double mplus  = (pip.momentum()+K0.momentum() ).mass2();
57      	double mpipi  = (pip.momentum()+pim.momentum()).mass2();
58       	_h[imode][0]->fill(mplus );
59       	_h[imode][1]->fill(mminus);
60       	_h[imode][2]->fill(mpipi );
61      }
62    }
63
64
65    /// Normalise histograms etc., after the run
66    void finalize() {
67      for(unsigned int ix=0;ix<2;++ix)
68	for(unsigned int iy=0;iy<3;++iy)
69	  normalize(_h[ix][iy],1.,false);
70    }
71
72    /// @}
73
74
75    /// @name Histograms
76    /// @{
77    Histo1DPtr _h[2][3];
78    /// @}
79
80
81  };
82
83
84  RIVET_DECLARE_PLUGIN(BESIII_2022_I2615968);
85
86}