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BELLE_2007_I753243

$K_S^0\pi^-$ spectrum in $\tau$ decays
Experiment: BELLE (KEKB)
Inspire ID: 753243
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Lett. B654 (2007) 65-73
Beams: * *
Beam energies: ANY
Run details:
  • e+ e- > tau+ tau-, or any process producing tau leptons

Measurement of the spectrum of $K_S^0\pi^-$ spectrum in $\tau$ decays by BELLE. Useful for testing models of the hadronic current in $\tau$ decays.

Source code: BELLE_2007_I753243.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Add a short analysis description here
 9  class BELLE_2007_I753243 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I753243);
14
15
16    /// @name Analysis methods
17    //@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21
22      declare(UnstableParticles(), "UFS");
23      book(_hist_Kpi, 1, 1, 1);
24
25    }
26
27    void findDecayProducts(const Particle & mother, unsigned int & nstable,
28                           unsigned int & npip, unsigned int & npim,
29                           unsigned int & nK, FourMomentum & ptot) {
30      for(const Particle & p : mother.children()) {
31        int id = p.pid();
32        if (id == PID::K0S ) {
33	  ++nK;
34          ++nstable;
35	  ptot += p.momentum();
36	}
37        else if (id == PID::PIPLUS) {
38          ++npip;
39          ++nstable;
40	  ptot += p.momentum();
41        }
42        else if (id == PID::PIMINUS) {
43          ++npim;
44          ++nstable;
45	  ptot += p.momentum();
46        }
47        else if (id == PID::PI0 || id == PID::KPLUS ||
48		 id == PID::KMINUS) {
49          ++nstable;
50        }
51        else if ( !p.children().empty() ) {
52          findDecayProducts(p, nstable, npip, npim, nK,ptot);
53        }
54        else
55          ++nstable;
56      }
57    }
58
59    /// Perform the per-event analysis
60    void analyze(const Event& event) {
61
62      // Loop over taus
63      for(const Particle& tau : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==PID::TAU)) {
64        unsigned int nstable(0),npip(0),npim(0),nK(0);
65	FourMomentum p_tot(0,0,0,0);
66        findDecayProducts(tau, nstable, npip, npim, nK, p_tot);
67        if (tau.pid() < 0) swap(npip, npim);
68	if(nstable==3 && npim==1 && nK==1)
69          _hist_Kpi->fill(p_tot.mass());
70      }
71    }
72
73
74    /// Normalise histograms etc., after the run
75    void finalize() {
76
77      normalize(_hist_Kpi);
78    }
79
80    //@}
81
82
83    /// @name Histograms
84    //@{
85    Histo1DPtr _hist_Kpi;
86    //@}
87
88
89  };
90
91
92  // The hook for the plugin system
93  RIVET_DECLARE_PLUGIN(BELLE_2007_I753243);
94
95
96}