Rivet analyses

π+π− mass distribution in B0 → π+π−K*0 decays

Experiment: BABAR (PEP-II)

Inspire ID: 1081760

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 85 (2012) 072005

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0, originally Upsilon(4S) decays

Measurement of the π+π− mass distribution in B0 → π+π−K*0 decays. The other distriubutions in the paper are designed solely to isolate various resonant components and are therefore not implemented.

Source code:BABAR_2012_I1081760.cc

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

namespace Rivet {


  /// @brief B0 -> pi+ pi- K*0
  class BABAR_2012_I1081760 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1081760);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(313);
      B0.addStable(-313);
      declare(B0, "B0");
      // histogram
      book(_h, 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{211, 1}, {-211, 1}, {313, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{211, 1}, {-211, 1}, {-313, 1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
        int sign = 1;
        if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode))
          sign = 1;
        else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, modeCC))
          sign = -1;
        else
          continue;
        const Particle& pip = B0.decayProducts()[ix].at(sign * 211)[0];
        const Particle& pim = B0.decayProducts()[ix].at(-sign * 211)[0];
        _h->fill((pip.momentum() + pim.momentum()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2012_I1081760);

}