Rivet analyses

title: ARGUS_1987_I238071

$\pi^+\pi^-$ mass spectrum in $\Upsilon(2S)\to\pi^+\pi^-\Upsilon(1S)$

Experiment: ARGUS (DORIS)

Inspire ID: 238071

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Z.Phys.C 35 (1987) 283

Beams: * *

Beam energies: ANY

Run details: - In princple any process producing Upsilon(2S)

Measurement of the $\pi^+\pi^-$ mass spectrum in $\Upsilon(2S)\to\pi^+\pi^-\Upsilon(1S)$.

Source code:ARGUS_1987_I238071.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Upsilon(2S) -> Upsilon(1S) pi+pi- class ARGUS_1987_I238071 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1987_I238071);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 100553);
  declare(ufs, "UFS");
  DecayedParticles UPS(ufs);
  UPS.addStable(553);
  declare(UPS, "UPS");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h[ix], 1 + ix, 1, 1);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles UPS = apply<DecayedParticles>(event, "UPS");
  // loop over particles
  for (unsigned int ix = 0; ix < UPS.decaying().size(); ++ix) {
    // check pi+pi- upslion(1S) decay mode
    if (!UPS.modeMatches(ix, 3, mode)) continue;
    const Particle& ups1 = UPS.decayProducts()[ix].at(553)[0];
    const Particle& pip = UPS.decayProducts()[ix].at(211)[0];
    const Particle& pim = UPS.decayProducts()[ix].at(-211)[0];
    double mpipi = (pip.momentum() + pim.momentum()).mass();
    _h[0]->fill(mpipi);
    double mpi = pip.mass() + pim.mass();
    double x = (mpipi - mpi) / (UPS.decaying()[ix].mass() - ups1.mass() - mpi);
    _h[1]->fill(x);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
const map<PdgId, unsigned int> mode = {{553, 1}, {211, 1}, {-211, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(ARGUS_1987_I238071);

} ```