Rivet analyses referenceBABAR_2005_I651834$\pi^+\pi^-$ mass distribution in $X(3872$ and $\psi(2S)$ to $J/\psi\pi^+\pi^-$Experiment: BABAR (PEP-II) Inspire ID: 651834 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
The $\pi^+\pi^-$ mass distribution in the decays $X(3872$ and $\psi(2S)$ to $J/\psi\pi^+\pi^-$ measureed by BaBaR in $B\to J\psi K^-\pi^+\pi^-$ decays. The background subtracted data were read from figure 3 in the paper. There is no consensus as to the nature of the $\chi_{c1}(3872)$ $c\bar{c}$ 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_I651834.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)/X(3782) -> J/psi pi+pi-
10 class BABAR_2005_I651834 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I651834);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 // set the PDG code
23 _pid = getOption<int>("PID", 9030443);
24 // projections
25 UnstableParticles ufs = UnstableParticles(Cuts::abspid==100443 ||
26 Cuts::abspid==_pid);
27 declare(ufs, "UFS");
28 DecayedParticles PSI(ufs);
29 PSI.addStable(443);
30 declare(PSI, "PSI");
31 // histos
32 for(unsigned int ix=0;ix<2;++ix)
33 book(_h[ix],1+ix,1,1);
34 }
35
36
37 /// Perform the per-event analysis
38 void analyze(const Event& event) {
39 static const map<PdgId,unsigned int> & mode = { { 211,1}, {-211,1}, { 443,1}};
40 DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
41 for(unsigned int ix=0;ix<PSI.decaying().size();++ix) {
42 if(!PSI.modeMatches(ix,3,mode)) continue;
43 const Particle & pip = PSI.decayProducts()[ix].at( 211)[0];
44 const Particle & pim = PSI.decayProducts()[ix].at(-211)[0];
45 double mpipi = (pip.momentum()+pim.momentum()).mass();
46 _h[PSI.decaying()[ix].pid()==_pid ? 0 : 1]->fill(mpipi);
47 }
48 }
49
50
51 /// Normalise histograms etc., after the run
52 void finalize() {
53 for(unsigned int ix=0;ix<2;++ix)
54 normalize(_h[ix],1.,false);
55 }
56
57 /// @}
58
59
60 /// @name Histograms
61 /// @{
62 int _pid;
63 Histo1DPtr _h[2];
64 /// @}
65
66
67 };
68
69
70 RIVET_DECLARE_PLUGIN(BABAR_2005_I651834);
71
72}
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