Rivet analyses

Mass distributions in B+ → π+π0π0

Experiment: BELLE (KEKB)

Inspire ID: 2131772

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2208.01855

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+ mesons, originally Upsilon(4S) decays

Measurement of the π+π0 and π0π0 mass distributions in B+ → π+π0π0. The background subtracted, corrected data was read from the plots in the paper

Source code:BELLE_2022_I2131772.cc

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

namespace Rivet {


  /// @brief B+ -> pi+ pi0 pi0
  class BELLE_2022_I2131772 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2022_I2131772);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==521);
      declare(ufs, "UFS");
      DecayedParticles BP(ufs);
      BP.addStable( 111);
      declare(BP, "BP");
      // histos
      for (unsigned int ix=0;ix<2;++ix) {
        book(_h[ix],1,1,1+ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      for (unsigned int ix=0; ix<BP.decaying().size(); ++ix) {
        int sign = 1;
        if (BP.decaying()[ix].pid()>0 && BP.modeMatches(ix,3,mode))        sign= 1;
        else if (BP.decaying()[ix].pid()<0 && BP.modeMatches(ix,3,modeCC)) sign=-1;
        else continue;
        const Particle & pip = BP.decayProducts()[ix].at( sign*211)[0];
        const Particles& pi0 = BP.decayProducts()[ix].at(      111);
        double mpip[2] = {(pip.mom()+pi0[0].mom()).mass(),
                          (pip.mom()+pi0[1].mom()).mass()};
        _h[0]->fill(min(mpip[0],mpip[1]));
        _h[1]->fill((pi0[0].mom()+pi0[1].mom()).mass());
      }
    }


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

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(BELLE_2022_I2131772);

}