Rivet analyses

Mass distributions in B+ → pp̄K+

Experiment: BABAR (PEP-II)

Inspire ID: 686573

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 72 (2005) 051101

Beams: * *

Beam energies: ANY

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

Measurement of mass distributions in B+ → pp̄K+. The data were read from the plots in the paper and the backgrounds given subtracted.

Source code:BABAR_2005_I686573.cc

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

namespace Rivet {


  /// @brief B+ -> p pbar K+
  class BABAR_2005_I686573 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2005_I686573);


    /// @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(10441);
      BP.addStable(10443);
      BP.addStable(20443);
      BP.addStable(100443);
      BP.addStable(441);
      BP.addStable(445);
      declare(BP, "BP");
      // histos
      book(_h_pp, 1, 1, 1);
      for (unsigned int ix = 0; ix < 2; ++ix) book(_h_pK[ix], 2, 1, 1 + ix);
      book(_c, "TMP/nB");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{2212, 1}, {-2212, 1}, {321, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{2212, 1}, {-2212, 1}, {-321, 1}};
      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, mode1))
          sign = 1;
        else if (BP.modeMatches(ix, 3, mode1CC))
          sign = -1;
        else
          continue;
        _c->fill();
        const Particle& pp = BP.decayProducts()[ix].at(sign * 2212)[0];
        const Particle& pbar = BP.decayProducts()[ix].at(-sign * 2212)[0];
        const Particle& Kp = BP.decayProducts()[ix].at(sign * 321)[0];
        _h_pp->fill((pp.momentum() + pbar.momentum()).mass());
        double mpK = (Kp.momentum() + pp.momentum()).mass();
        double mpbarK = (Kp.momentum() + pbar.momentum()).mass();
        if (mpK > mpbarK)
          _h_pK[0]->fill(mpK);
        else
          _h_pK[1]->fill(mpbarK);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h_pp, 1. / *_c);
      for (unsigned int ix = 0; ix < 2; ++ix) scale(_h_pK[ix], 1. / *_c);
      Histo1DPtr tmp;
      book(tmp, 2, 1, 3);
      *tmp = *_h_pK[0] - *_h_pK[1];
      tmp->setPath("/" + name() + "/" + mkAxisCode(2, 1, 3));
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_pp, _h_pK[2];
    CounterPtr _c;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2005_I686573);

}