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ARGUS_1992_I335698

Hadronic mass spectrum and helicity angle in $\tau^-\to\pi^-\pi^0\nu_\tau$
Experiment: ARGUS (DORIS)
Inspire ID: 335698
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Z.Phys.C 56 (1992) 339-346
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing tau leptons, originally e+e-

Hadronic mass spectrum and helicity angle in $\tau^-\to\pi^-\pi^0\nu_\tau$. Corrected data read from figures 3 and 4 in the paper.

Source code: ARGUS_1992_I335698.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 tau -> pi- pi0 nu_tau
10  class ARGUS_1992_I335698 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1992_I335698);
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==15);
24      declare(ufs, "UFS");
25      DecayedParticles TAU(ufs);
26      TAU.addStable(310);
27      TAU.addStable(111);
28      TAU.addStable(221);
29      declare(TAU, "TAU");
30      // hists
31      for (unsigned int ix=0; ix<2; ++ix) {
32        book(_h[ix], 1+ix, 1, 1);
33      }
34    }
35
36
37    /// Perform the per-event analysis
38    void analyze(const Event& event) {
39      DecayedParticles TAU = apply<DecayedParticles>(event, "TAU");
40      // loop over particles
41      for (unsigned int ix=0; ix<TAU.decaying().size(); ++ix) {
42      	int sign = TAU.decaying()[ix].pid()>0 ? 1 : -1;
43      	if (!(TAU.modeMatches(ix,3,mode) || TAU.modeMatches(ix,3,modeCC))) continue;
44        const Particle& pi0 = TAU.decayProducts()[ix].at( 111     )[0];
45        const Particle& pim = TAU.decayProducts()[ix].at(-211*sign)[0];
46        FourMomentum phad = pim.mom()+pi0.mom();
47        _h[0]->fill(phad.mass());
48        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(phad.betaVec());
49        FourMomentum ppi = boost.transform(pim.mom());
50        const double cTheta = ppi.p3().unit().dot(phad.p3().unit());
51        _h[1]->fill(cTheta);
52      }
53    }
54
55
56    /// Normalise histograms etc., after the run
57    void finalize() {
58      normalize(_h, 1.0, false);
59    }
60
61    /// @}
62
63
64    /// @name Histograms
65    /// @{
66    Histo1DPtr _h[2];
67    const map<PdgId,unsigned int> mode   = { { 111,1},{-211,1},{ 16,1}};
68    const map<PdgId,unsigned int> modeCC = { { 111,1},{ 211,1},{-16,1}};
69    /// @}
70
71
72  };
73
74
75  RIVET_DECLARE_PLUGIN(ARGUS_1992_I335698);
76
77}