Rivet analyses

title: CLEOII_1996_I415409

Hadronic mass in $\tau^-\to K^-\eta\nu_\tau$

Experiment: CLEOII (CESR)

Inspire ID: 415409

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 76 (1996) 4119-4123

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 $K^-\eta$ system in $\tau\to K^-\eta\nu_\tau$ measured by CLEO at CESR.

Source code:CLEOII_1996_I415409.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief tau -> K eta class CLEOII_1996_I415409 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1996_I415409);


/// @name Analysis methods
/// @{

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(), "UFS");
  book(_hist, 1, 1, 1);
}

void findDecayProducts(const Particle& mother, unsigned int& nstable, Particles& eta, Particles& K) {
  for (const Particle& p : mother.children()) {
    long id = p.abspid();
    if (id == PID::ETA) {
      eta.push_back(p);
      ++nstable;
    }
    else if (id == PID::KPLUS) {
      K.push_back(p);
      ++nstable;
    }
    else if (!p.children().empty()) {
      findDecayProducts(p, nstable, eta, K);
    }
    else
      ++nstable;
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles(Cuts::abspid == PID::TAU)) {
    Particles eta, K;
    unsigned int nstable = 0;
    // find the decay products we want
    findDecayProducts(p, nstable, eta, K);
    if (nstable != 3) continue;
    // K eta
    if (K.size() == 1 && eta.size() == 1) _hist->fill((eta[0].momentum() + K[0].momentum()).mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_hist);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _hist;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_1996_I415409);

} ```