Rivet analyses

title: BESII_2005_I663288

Mass distributions in $J/\psi\to\phi\pi^+\pi^+$ and $\phi K^+K^-$

Experiment: BESII (BEPC)

Inspire ID: 663288

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 607 (2005) 243-253

Beams: * *

Beam energies: ANY

Run details: - Any process producing J/psi, originally e+e-

Mass distributions in $J/\psi\to\phi\pi^+\pi^+$ and $\phi K^+K^-$. The data were read from the figures in the paper and are not corrected for acceptance.

Source code:BESII_2005_I663288.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/psi -> phi pi+pi- K+K- class BESII_2005_I663288 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESII_2005_I663288);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 443);
  declare(ufs, "UFS");
  DecayedParticles PSI(ufs);
  PSI.addStable(333);
  declare(PSI, "PSI");
  // histograms
  for (unsigned int ix = 0; ix < 2; ++ix) {
    for (unsigned int iy = 0; iy < 2; ++iy) {
      book(_h_mass[ix][iy], 1 + ix, 1, 1 + iy);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // J/psi decay products
  DecayedParticles PSI = apply<DecayedParticles>(event, "PSI");
  if (PSI.decaying().size() != 1) vetoEvent;
  unsigned int imode = 0;
  if (PSI.modeMatches(0, 3, mode1))
    imode = 0;
  else if (PSI.modeMatches(0, 3, mode2))
    imode = 1;
  else
    vetoEvent;
  unsigned int iMeson = imode == 0 ? 211 : 321;
  const Particle& Mp = PSI.decayProducts()[0].at(iMeson)[0];
  const Particle& Mm = PSI.decayProducts()[0].at(-iMeson)[0];
  const Particle& phi = PSI.decayProducts()[0].at(333)[0];
  // mass histograms
  FourMomentum pX = Mp.momentum() + Mm.momentum();
  const double mX = pX.mass();
  _h_mass[imode][0]->fill(mX / GeV);
  _h_mass[imode][1]->fill((Mp.momentum() + phi.momentum()).mass() / GeV);
  _h_mass[imode][1]->fill((Mm.momentum() + phi.momentum()).mass() / GeV);
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 2; ++ix) {
    normalize(_h_mass[ix], 1.0, false);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[2][2];
const map<PdgId, unsigned int> mode1 = {{333, 1}, {211, 1}, {-211, 1}};
const map<PdgId, unsigned int> mode2 = {{333, 1}, {321, 1}, {-321, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BESII_2005_I663288);

} ```