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CLEOII_1995_I400623

Spectral functions in $\tau^-\to\pi^-\pi^-\pi^+\pi^0\nu_\tau$
Experiment: CLEOII (CESR)
Inspire ID: 400623
Status: VALIDATED NOHEPDATA
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 75 (1995) 3809-3813
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing tau leptons, originally e+e-

Measurement of the spectral functions for $\tau^-\to\pi^-\pi^-\pi^+\pi^0\nu_\tau$ and $\tau^-\to\pi^-\omega\nu_\tau$, and the helicity angle in $\tau^-\to\pi^-\omega\nu_\tau$. The corrected data were read from figure 3b in the paper.

Source code: CLEOII_1995_I400623.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- pi- pi+ pi0
10  class CLEOII_1995_I400623 : public Analysis {
11  public:
12
13    /// Constructor
14    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1995_I400623);
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      // histograms
31      for (unsigned int ix=0; ix<2; ++ix) {
32        book(_h_spect[ix], 1, 1, 1+ix);
33      }
34      book(_c,"TMP/nTau");
35    }
36
37
38    /// Perform the per-event analysis
39    void analyze(const Event& event) {
40      DecayedParticles TAU = apply<DecayedParticles>(event, "TAU");
41      // loop over particles
42      for (unsigned int ix=0; ix<TAU.decaying().size(); ++ix) {
43        _c->fill();
44      	int sign = TAU.decaying()[ix].pid()>0 ? 1 : -1;
45      	if (!(TAU.modeMatches(ix,5,mode) || TAU.modeMatches(ix,5,modeCC))) continue;
46        const Particle&  pi0 = TAU.decayProducts()[ix].at( 111     )[0];
47        const Particles& pim = TAU.decayProducts()[ix].at(-211*sign);
48        const Particle&  pip = TAU.decayProducts()[ix].at( 211*sign)[0];
49        FourMomentum phad = pim[0].mom()+pim[1].mom()+pip.mom()+pi0.mom();
50        const double q = phad.mass();
51        const double mtau = TAU.decaying()[ix].mass();
52        _h_spect[0]->fill(phad.mass(),sqr(mtau)*mtau/q/sqr(sqr(mtau)-sqr(q))/(sqr(mtau)+2.*sqr(q)));
53        Particle omega;
54        int iomega=-1;
55        for (unsigned int ix=0; ix<2; ++ix) {
56          Particle parent = pim[ix];
57          while (!parent.parents().empty()) {
58            parent = parent.parents()[0];
59            if (parent.pid()==223) break;
60          }
61          if (parent.pid()==223) {
62            omega=parent;
63            iomega=ix;
64          }
65        }
66        if (iomega<0) continue;
67        _h_spect[1]->fill(phad.mass(),sqr(mtau)*mtau/q/sqr(sqr(mtau)-sqr(q))/(sqr(mtau)+2.*sqr(q)));
68      }
69    }
70
71
72    /// Normalise histograms etc., after the run
73    void finalize() {
74      const double Gamma = 6.582119514e-25/290.3e-15;
75      const double GF    = 1.1663787e-5;
76      const double cosC  = 0.97373;
77      scale(_h_spect, Gamma*16.*sqr(M_PI)/sqr(GF*cosC)/ *_c);
78    }
79
80    /// @}
81
82
83    /// @name Histograms
84    /// @{
85    Histo1DPtr _h_spect[2];
86    CounterPtr _c;
87    const map<PdgId,unsigned int> mode   = { { 111,1},{-211,2},{ 211,1},{ 16,1}};
88    const map<PdgId,unsigned int> modeCC = { { 111,1},{ 211,2},{-211,1},{-16,1}};
89    /// @}
90
91
92  };
93
94
95  RIVET_DECLARE_PLUGIN(CLEOII_1995_I400623);
96
97}