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## Rivet analyses reference

### CLEO_1999_I508944

Measurement of Semi-Leptonic Tau Decays into $\pi^\pm\pi^0$
Experiment: CLEO (CESR)
Inspire ID: 508944
Status: VALIDATED
Authors:
• Peter Richardson
References:
• Phys.Rev. D61 (2000) 112002
• hep-ex/9910046
Beams: * *
Beam energies: ANY
Run details:
• Tau production, can be any process but original data was in $e^+ e^-$ at the $\Upsilon(4S)$ resonance

Measurement of the invariant mass spectrum of the $\pi^-\pi^0$ system in $\tau\to\pi^-\pi^0\nu_\tau$ measured by CLEO at CESR.

Source code: CLEO_1999_I508944.cc
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/UnstableParticles.hh" namespace Rivet { /// @brief tau -> pi-pi0 nu_tau class CLEO_1999_I508944 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(CLEO_1999_I508944); /// @name Analysis methods //@{ /// Book histograms and initialise projections before the run void init() { declare(UnstableParticles(), "UFS"); book(_hist_pipi, 1, 1, 1); } /// Perform the per-event analysis void analyze(const Event& event) { // Find the taus Particles taus; const UnstableParticles& ufs = apply(event, "UFS"); for (const Particle& p : ufs.particles()) { if (p.abspid() != PID::TAU) continue; Particles pip, pim, pi0; unsigned int nstable = 0; // get the boost to the rest frame // find the decay products we want findDecayProducts(p, nstable, pip, pim, pi0); if (p.pid() < 0) { swap(pip, pim); } if (nstable != 3) continue; // pipi if (pim.size() == 1 && pi0.size() == 1) _hist_pipi->fill((pi0[0].momentum()+pim[0].momentum()).mass()); } } void findDecayProducts(const Particle & mother, unsigned int & nstable, Particles& pip, Particles& pim, Particles& pi0) { for(const Particle & p : mother.children()) { long id = p.pid(); if (id == PID::PI0 ) { pi0.push_back(p); ++nstable; } else if (id == PID::PIPLUS) { pip.push_back(p); ++nstable; } else if (id == PID::PIMINUS) { pim.push_back(p); ++nstable; } else if (id == PID::K0S || id == PID::KPLUS || id == PID::KMINUS) { ++nstable; } else if ( !p.children().empty() ) { findDecayProducts(p, nstable, pip, pim, pi0); } else ++nstable; } } /// Normalise histograms etc., after the run void finalize() { normalize(_hist_pipi); } //@} /// @name Histograms //@{ Histo1DPtr _hist_pipi; //@} }; // The hook for the plugin system DECLARE_RIVET_PLUGIN(CLEO_1999_I508944); }