Rivet analyses

π⁺π⁻ mass distriubution in B⁺ → π⁺π⁺π⁻

Experiment: BABAR (PEP-II)

Inspire ID: 813140

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 79 (2009) 072006

Beams: * *

Beam energies: ANY

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

Measurement of the π⁺π⁻ mass distriubutions in B⁺ → π⁺π⁺π⁻. The data were read from the plotsi in the paper and may not be corrected for efficiency/acceptable, although the backgrounds given in the paper have been subtracted.

Source code:`BABAR_2009_I813140.cc`

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

namespace Rivet {


  /// @brief B+ -> pi+ pi+ pi-
  class BABAR_2009_I813140 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I813140);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BP(ufs);
      declare(BP, "BP");
      // histograms
      book(_h_all, 1, 1, 1);
      for (unsigned int ix = 0; ix < 3; ++ix)
        for (unsigned int iy = 0; iy < 2; ++iy) book(_h_charge[ix][iy], 2, 1 + ix, 1 + iy);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{-211, 1}, {211, 2}};
      static const map<PdgId, unsigned int>& modeCC = {{211, 1}, {-211, 2}};
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      // loop over particles
      for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
        int sign = 1;
        if (BP.modeMatches(ix, 3, mode))
          sign = 1;
        else if (BP.modeMatches(ix, 3, modeCC))
          sign = -1;
        else
          continue;
        // particles
        const Particle& pim = BP.decayProducts()[ix].at(-sign * 211)[0];
        const Particles& pip = BP.decayProducts()[ix].at(sign * 211);
        // boost to B rest frame
        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
            BP.decaying()[ix].momentum().betaVec());
        FourMomentum pPim = boost.transform(pim.momentum());
        FourMomentum pPip[2];
        for (unsigned int ix = 0; ix < 2; ++ix) pPip[ix] = boost.transform(pip[ix].momentum());
        // loop over pi+
        for (unsigned int ix = 0; ix < 2; ++ix) {
          FourMomentum ppipi = pip[ix].momentum() + pim.momentum();
          double mpipi = ppipi.mass();
          _h_all->fill(mpipi);
          _h_charge[0][(1 - sign) / 2]->fill(mpipi);
          unsigned int ibatch = ix == 0 ? 1 : 0;
          Vector3 axis = pPip[ibatch].p3().unit();
          LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
          Vector3 axis2 = boost1.transform(pPim).p3().unit();
          double cTheta = axis.dot(axis2);
          if (cTheta > 0) {
            _h_charge[1][(1 - sign) / 2]->fill(mpipi);
          }
          else {
            _h_charge[2][(1 - sign) / 2]->fill(mpipi);
          }
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h_all, 1., false);
      for (unsigned int ix = 0; ix < 3; ++ix)
        for (unsigned int iy = 0; iy < 2; ++iy) normalize(_h_charge[ix][iy], 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_all, _h_charge[3][2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2009_I813140);

}

Rivet analyses

π+π− mass distriubution in B+ → π+π+π−

Source code:BABAR_2009_I813140.cc

π⁺π⁻ mass distriubution in B⁺ → π⁺π⁺π⁻

Source code:`BABAR_2009_I813140.cc`