Rivet analyses

Mass distributions in B⁺ → K⁺π⁺π⁻

Experiment: BABAR (PEP-II)

Inspire ID: 782405

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 78 (2008) 071103

Beams: * *

Beam energies: ANY

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

Measurement of mass distributions in B⁺ → K⁺π⁺π⁻. The data were read from the figures in the paper and the backgrounds given subtracted.

Source code:`BABAR_2008_I782405.cc`

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

namespace Rivet {


  /// @brief B -> K pi pi
  class BABAR_2008_I782405 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I782405);


    /// @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);
      BP.addStable(PID::K0S);
      declare(BP, "BP");
      // histos
      for (unsigned int iy = 0; iy < 3; ++iy) {
        book(_h_mass[iy], 1, 1, 1 + iy);
        for (unsigned int ix = 0; ix < 2; ++ix) book(_h_mass2[ix][iy], 2, 1 + iy, 1 + ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{321, 1}, {211, 1}, {-211, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {211, 1}, {-211, 1}};
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      // loop over particles
      for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
        int sign = BP.decaying()[ix].pid() > 0 ? 1 : -1;
        if ((sign > 0 and BP.modeMatches(ix, 3, mode)) || (sign < 0 and BP.modeMatches(ix, 3, modeCC))) {
          LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
              BP.decaying()[ix].momentum().betaVec());
          // momenta
          FourMomentum pip = boost.transform(BP.decayProducts()[ix].at(211 * sign)[0].momentum());
          FourMomentum pim = boost.transform(BP.decayProducts()[ix].at(-211 * sign)[0].momentum());
          FourMomentum Kp = boost.transform(BP.decayProducts()[ix].at(321 * sign)[0].momentum());
          // mass distributions
          double mKpi = (Kp + pim).mass();
          double mpipi = (pip + pim).mass();
          // vetos
          if (mKpi > 1.756 && mKpi < 1.931) continue;
          if (mpipi > 1.660 && mpipi < 1.800) continue;
          if (mpipi > 3.019 && mpipi < 3.179) continue;
          if (mpipi > 3.627 && mpipi < 3.747) continue;
          // mass distributions
          if (mpipi > 2.) _h_mass[0]->fill(mKpi);
          if (mKpi > 2.) {
            _h_mass[1]->fill(mpipi);
            _h_mass[2]->fill(mpipi);
          }
          FourMomentum ppipi = pim + pip;
          LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(ppipi.betaVec());
          double cTheta = boost2.transform(pim).p3().unit().dot(Kp.p3().unit());
          _h_mass2[(sign + 1) / 2][0]->fill(mpipi);
          if (cTheta > 0)
            _h_mass2[(sign + 1) / 2][1]->fill(mpipi);
          else
            _h_mass2[(sign + 1) / 2][2]->fill(mpipi);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int iy = 0; iy < 3; ++iy) {
        normalize(_h_mass[iy], 1., false);
        for (unsigned int ix = 0; ix < 2; ++ix) normalize(_h_mass2[ix][iy], 1., false);
      }
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_mass[3], _h_mass2[2][3];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2008_I782405);

}

Rivet analyses

Mass distributions in B+ → K+π+π−

Source code:BABAR_2008_I782405.cc

Mass distributions in B⁺ → K⁺π⁺π⁻

Source code:`BABAR_2008_I782405.cc`