Rivet analyses

B0 → pp̄π0

Experiment: BELLE (KEKB)

Inspire ID: 1729311

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 99 (2019) 9, 091104

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0 originally e+e- at Upsilon(4S)

Measurement of the mass distributions in the decay B0 → pp̄π0. The data were read from the plots in the paper, but is corrected for detector efficiency.

Source code:BELLE_2019_I1729311.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief B0 -> p pbar pi0
  class BELLE_2019_I1729311 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2019_I1729311);


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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(PID::PI0);
      B0.addStable(PID::K0S);
      B0.addStable(PID::ETA);
      B0.addStable(PID::ETAPRIME);
      declare(B0, "B0");
      book(_h[0], 1, 1, 1);
      for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix + 1], 2, 1, 1 + ix);
      book(_dalitz, "dalitz", 50, 1., 20., 50, 1., 20.);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{2212, 1}, {-2212, 1}, {111, 1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
        if (!B0.modeMatches(ix, 3, mode)) continue;
        int sign = B0.decaying()[ix].pid() / 511;
        const Particle& pi0 = B0.decayProducts()[ix].at(111)[0];
        const Particle& pp = B0.decayProducts()[ix].at(sign * 2212)[0];
        const Particle& pbar = B0.decayProducts()[ix].at(-sign * 2212)[0];
        double mminus = (pbar.momentum() + pi0.momentum()).mass2();
        double mplus = (pp.momentum() + pi0.momentum()).mass2();
        _h[0]->fill((pp.momentum() + pbar.momentum()).mass());
        _h[1]->fill(sqrt(mplus));
        _h[2]->fill(sqrt(mminus));
        _dalitz->fill(mplus, mminus);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_dalitz);
      for (unsigned int ix = 0; ix < 3; ++ix) normalize(_h[ix]);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3];
    Histo2DPtr _dalitz;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2019_I1729311);

}