Rivet analyses

title: CLEOII_1999_I501487

Mass distributions in $\tau^-\to\pi^-\pi^-\pi^+\pi^0\nu_\tau$

Experiment: CLEOII (CESR)

Inspire ID: 501487

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 61 (2000) 052002

Beams: * *

Beam energies: ANY

Run details: none listed

Mass distributions in $\tau^-\to\pi^-\pi^-\pi^+\pi^0\nu_\tau$. The data were read from figures 2 and 3 in the paper and may not be fully corrected..

Source code:CLEOII_1999_I501487.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief tau -> pi- pi- pi+ pi0 class CLEOII_1999_I501487 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1999_I501487);


/// @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");
  // histograms
  for (unsigned int ix = 0; ix < 3; ++ix) {
    book(_h_2pi[ix], 1, 1, 1 + ix);
    if (ix == 2) continue;
    book(_h_4pi[ix], 2, 1, 1 + ix);
  }
}


/// 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& pi0 = TAU.decayProducts()[ix].at(111)[0];
    const Particles& pim = TAU.decayProducts()[ix].at(-211 * sign);
    const Particle& pip = TAU.decayProducts()[ix].at(211 * sign)[0];
    Particle omega;
    int iomega = -1;
    for (unsigned int ix = 0; ix < 2; ++ix) {
      Particle parent = pim[ix];
      while (!parent.parents().empty()) {
        parent = parent.parents()[0];
        if (parent.pid() == 223) break;
      }
      if (parent.pid() == 223) {
        omega = parent;
        iomega = ix;
      }
    }
    FourMomentum phad = pim[0].mom() + pim[1].mom() + pip.mom() + pi0.mom();
    const double q = phad.mass();
    if (iomega > 0) {
      _h_4pi[0]->fill(q);
    }
    else {
      _h_4pi[1]->fill(q);
      _h_2pi[0]->fill((pi0.mom() + pip.mom()).mass());
      for (unsigned int iy = 0; iy < 2; ++iy) {
        _h_2pi[1]->fill((pim[iy].mom() + pi0.mom()).mass());
        _h_2pi[2]->fill((pim[iy].mom() + pip.mom()).mass());
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_2pi, 1.0, false);
  normalize(_h_4pi, 1.0, false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_2pi[3], _h_4pi[2];
const map<PdgId, unsigned int> mode = {{111, 1}, {-211, 2}, {211, 1}, {16, 1}};
const map<PdgId, unsigned int> modeCC = {{111, 1}, {211, 2}, {-211, 1}, {-16, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_1999_I501487);

} ```