Rivet analyses referenceBABAR_2005_I686354$\pi^+\pi^-$ mass distribution in $Y(4260)\to J/\psi\pi^+\pi^-$Experiment: BABAR (PEP-II) Inspire ID: 686354 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Mass distribution in $Y(4260)\to J/\psi\pi^+\pi^-$ decays ($Y(4260)$ is now $\psi(4230)$). The background subtracted data were read from figure 3 in the paper. There is no consensus as to the nature of the $\psi(4230)$ $c\bar{c}$ state and therefore we taken its PDG code to be 9030443, i.e. the first unused code for an undetermined spin one $c\bar{c}$ state. This can be changed using the PID option if a different code is used by the event generator performing the simulation. Source code: BABAR_2005_I686354.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 Y(4260) -> pi+ pi_ J/psi
10 class BABAR_2005_I686354 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I686354);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 _pid = getOption<int>("PID", 9030443);
23 // projections
24 UnstableParticles ufs = UnstableParticles(Cuts::abspid==_pid);
25 declare(ufs, "UFS");
26 DecayedParticles PSI(ufs);
27 PSI.addStable(443);
28 declare(PSI, "PSI");
29 // histograms
30 book(_h,1,1,1);
31 }
32
33
34 /// Perform the per-event analysis
35 void analyze(const Event& event) {
36 static const map<PdgId,unsigned int> & mode = { { 211,1}, {-211,1}, { 443,1}};
37 DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
38 for(unsigned int ix=0;ix<PSI.decaying().size();++ix) {
39 if (!PSI.modeMatches(ix,3,mode)) continue;
40 const Particle & pip = PSI.decayProducts()[ix].at( 211)[0];
41 const Particle & pim = PSI.decayProducts()[ix].at(-211)[0];
42 double mpipi = (pip.momentum()+pim.momentum()).mass();
43 _h->fill(mpipi);
44 }
45 }
46
47 /// Normalise histograms etc., after the run
48 void finalize() {
49 normalize(_h,1.,false);
50 }
51
52 /// @}
53
54
55 /// @name Histograms
56 /// @{
57 int _pid;
58 Histo1DPtr _h;
59 /// @}
60
61
62 };
63
64
65 RIVET_DECLARE_PLUGIN(BABAR_2005_I686354);
66
67}
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