Rivet analyses referenceBESIII_2017_I1511280Mass distributions in the decay D0→K−π+π+π−Experiment: BESIII (BEPC) Inspire ID: 1511280 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the mass distributions in the decay D0→K−π+π+π− by BES. The data were read from the plots in the paper and therefore for some points the error bars are the size of the point. It is also not clear that any resolution effects have been unfolded. Source code: BESIII_2017_I1511280.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 -> K- pi+ pi+ pi-
10 class BESIII_2017_I1511280 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2017_I1511280);
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<8;++ix)
33 book(_h[ix],1,1,1+ix);
34 }
35
36
37 /// Perform the per-event analysis
38 void analyze(const Event& event) {
39 // define the decay mode
40 static const map<PdgId,unsigned int> & mode = { {-321,1},{ 211,2}, {-211,1}};
41 static const map<PdgId,unsigned int> & modeCC = { { 321,1},{-211,2}, { 211,1}};
42 DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
43 // loop over particles
44 for(unsigned int ix=0;ix<D0.decaying().size();++ix) {
45 int sign = 1;
46 if (D0.decaying()[ix].pid()>0 && D0.modeMatches(ix,4,mode)) {
47 sign=1;
48 }
49 else if (D0.decaying()[ix].pid()<0 && D0.modeMatches(ix,4,modeCC)) {
50 sign=-1;
51 }
52 else
53 continue;
54 const Particles & Km = D0.decayProducts()[ix].at(-sign*321);
55 const Particles & pip= D0.decayProducts()[ix].at( sign*211);
56 const Particles & pim= D0.decayProducts()[ix].at(-sign*211);
57 // first pip gives higher pi+pi- mass
58 double mpipi[2] = {(pip[0].momentum()+pim[0].momentum()).mass(),
59 (pip[1].momentum()+pim[0].momentum()).mass()};
60 unsigned int i1= mpipi[0]>mpipi[1] ? 0 : 1;
61 unsigned int i2= i1==0 ? 1 : 0;
62 _h[0]->fill((Km [0].momentum()+pip[i1].momentum()).mass());
63 _h[1]->fill((Km [0].momentum()+pip[i2].momentum()).mass());
64 _h[2]->fill(sqr(mpipi[i1]));
65 _h[3]->fill(sqr(mpipi[i2]));
66 _h[4]->fill((Km [0].momentum()+pim[0].momentum()+pip[i1].momentum()).mass());
67 _h[5]->fill((Km [0].momentum()+pim[0].momentum()+pip[i2].momentum()).mass());
68 _h[6]->fill((pim[0].momentum()+pip[i1].momentum()+pip[i2].momentum()).mass());
69 _h[7]->fill((Km [0].momentum()+pip[i1].momentum()+pip[i2].momentum()).mass());
70 }
71 }
72
73
74 /// Normalise histograms etc., after the run
75 void finalize() {
76 for(unsigned int ix=0;ix<8;++ix)
77 normalize(_h[ix],1.,false);
78 }
79
80 /// @}
81
82
83 /// @name Histograms
84 /// @{
85 Histo1DPtr _h[8];
86 /// @}
87
88
89 };
90
91
92 RIVET_DECLARE_PLUGIN(BESIII_2017_I1511280);
93
94}
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