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E791_2001_I530319

Dalitz plot analysis of $D_s^+\to \pi^+\pi^+\pi^-$
Experiment: E791 (Fermilab)
Inspire ID: 530319
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 86 (2001) 765-769
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing D_s+ -> pi+ pi+ pi-

Measurement of the mass distributions in the decay $D_s^+\to \pi^+\pi^+\pi^-$. The data were read from the plots in the paper. Resolution/acceptance effects have been not unfolded and given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code: E791_2001_I530319.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 D_s+ -> pi+pi+pi-
10  class E791_2001_I530319 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(E791_2001_I530319);
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==431);
24      declare(ufs, "UFS");
25      DecayedParticles DS(ufs);
26      DS.addStable(PID::PI0);
27      DS.addStable(PID::K0S);
28      declare(DS,"DS");
29      // histos
30      book(_h_pi,1,1,1);
31      book(_dalitz, "dalitz",50,0.,3.5,50,0.0,3.5);
32    }
33
34    /// Perform the per-event analysis
35    void analyze(const Event& event) {
36      static const map<PdgId,unsigned int> & mode   = { { 211,2}, {-211,1}};
37      static const map<PdgId,unsigned int> & modeCC = { {-211,2}, { 211,1}};
38      DecayedParticles DS = apply<DecayedParticles>(event, "DS");
39      // loop over particles
40      for(unsigned int ix=0;ix<DS.decaying().size();++ix) {
41	int sign = 1;
42	if (DS.decaying()[ix].pid()>0 && DS.modeMatches(ix,3,mode)) {
43	  sign=1;
44	}
45	else if  (DS.decaying()[ix].pid()<0 && DS.modeMatches(ix,3,modeCC)) {
46	  sign=-1;
47	}
48	else
49	  continue;
50	const Particles & pip = DS.decayProducts()[ix].at( sign*211);
51	const Particle  & pim = DS.decayProducts()[ix].at(-sign*211)[0];
52	double m1 = (pim.momentum()+pip[0].momentum()).mass2();
53	double m2 = (pim.momentum()+pip[1].momentum()).mass2();
54	_h_pi->fill(m1);
55	_h_pi->fill(m2);
56	_dalitz->fill(m1,m2);
57	_dalitz->fill(m2,m1);
58      }
59    }
60
61
62    /// Normalise histograms etc., after the run
63    void finalize() {
64      normalize(_h_pi);
65      normalize(_dalitz);
66    }
67
68    /// @}
69
70
71    /// @name Histograms
72    /// @{
73    Histo1DPtr _h_pi;
74    Histo2DPtr _dalitz;
75    /// @}
76
77
78  };
79
80
81  RIVET_DECLARE_PLUGIN(E791_2001_I530319);
82
83}