Rivet analyses

title: CLEOII_1997_I444745

$\pi^+\pi^-\pi^-\eta$ mass in $\tau\to\pi^+\pi^-\pi^-\eta\nu_\tau$

Experiment: CLEOII (CESR)

Inspire ID: 444745

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 79 (1997) 2406-2410

Beams: * *

Beam energies: ANY

Run details: - Any process producing tau leptons, originally e+ e-

Measurement of the hadronic mass in $\tau\to\pi^+\pi^-\pi^-\eta\nu_\tau$ decays, excluding the $f_1$ contribution. The background subtracted data were read from figure 4 in the paper.

Source code:CLEOII_1997_I444745.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief tau -> pi+ pi- pi- eta nu_tau class CLEOII_1997_I444745 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1997_I444745);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 15);
  declare(ufs, "UFS");
  DecayedParticles TAU(ufs);
  TAU.addStable(310);
  TAU.addStable(111);
  TAU.addStable(221);
  declare(TAU, "TAU");
  // histogram
  book(_h, 1, 1, 1);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles TAU = apply<DecayedParticles>(event, "TAU");
  // loop over particles
  for (unsigned int ix = 0; ix < TAU.decaying().size(); ++ix) {
    int sign = TAU.decaying()[ix].pid() > 0 ? 1 : -1;
    if (!(TAU.modeMatches(ix, 5, mode) || TAU.modeMatches(ix, 5, modeCC))) continue;
    const Particle& pip = TAU.decayProducts()[ix].at(211 * sign)[0];
    const Particles& pim = TAU.decayProducts()[ix].at(-211 * sign);
    const Particle& eta = TAU.decayProducts()[ix].at(221)[0];
    FourMomentum phad = pip.mom() + eta.mom();
    bool hasF1 = false;
    for (unsigned int iy = 0; iy < 2; ++iy) {
      double mf1 = (phad + pim[iy].mom()).mass();
      hasF1 |= abs(mf1 - 1.2819) < 0.036;
    }
    if (hasF1) continue;
    phad += pim[0].mom() + pim[1].mom();
    _h->fill(phad.mass());
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1.0, false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h;
const map<PdgId, unsigned int> mode = {{221, 1}, {211, 1}, {-211, 2}, {16, 1}};
const map<PdgId, unsigned int> modeCC = {{221, 1}, {-211, 1}, {211, 2}, {-16, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_1997_I444745);

} ```