1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/UnstableParticles.hh"
  4
  5namespace Rivet {
  6
  7
  8  /// @brief B -> Xs gamma
  9  class BABAR_2012_I1122031 : public Analysis {
 10  public:
 11
 12    /// Constructor
 13    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1122031);
 14
 15
 16    /// @name Analysis methods
 17    /// @{
 18
 19    /// Book histograms and initialise projections before the run
 20    void init() {
 21      // Initialise and register projections
 22      declare(UnstableParticles(), "UFS");
 23      // Book histograms
 24      book(_h, 1, 1, 1);
 25      book(_nBottom, "TMP/BottomCounter");
 26    }
 27
 28    void findDecayProducts(const Particle& mother,
 29                           unsigned int& nK0, unsigned int& nKp, unsigned int& nKm,
 30                           FourMomentum& ptot) {
 31      for (const Particle & p : mother.children()) {
 32        int id = p.pid();
 33        if ( id == PID::KPLUS ) {
 34          ++nKp;
 35          ptot += p.momentum();
 36        }
 37        else if (id == PID::KMINUS ) {
 38          ++nKm;
 39          ptot += p.momentum();
 40        }
 41        else if (id == PID::K0S) {
 42          ++nK0;
 43          ptot += p.momentum();
 44        }
 45        else if (id == PID::PI0 || id == PID::PIPLUS || id == PID::PIMINUS) {
 46          ptot += p.momentum();
 47        }
 48        else if ( !p.children().empty() ) {
 49          findDecayProducts(p, nK0, nKp, nKm, ptot);
 50        }
 51        else
 52          ptot += p.momentum();
 53      }
 54    }
 55
 56    /// Perform the per-event analysis
 57    void analyze(const Event& event) {
 58      // Loop over bottoms
 59      for (const Particle& bottom : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==521 ||
 60										     Cuts::abspid==511)) {
 61	// remove mixing entries etc
 62	for (const Particle & child : bottom.children())
 63          if (child.abspid() == 511 || child.pid()==bottom.pid() ) continue;
 64        _nBottom->fill();
 65	FourMomentum pgamma(0.,0.,0.,0.);
 66	unsigned int ngamma = 0;
 67        for (const Particle & child : bottom.children()) {
 68	  if (child.pid() == PID::PHOTON) {
 69            ngamma += 1;
 70            pgamma += child.momentum();
 71          }
 72	}
 73	if (ngamma != 1) continue;
 74        unsigned int nK0(0),nKp(0),nKm(0);
 75        FourMomentum p_tot(0,0,0,0);
 76        findDecayProducts(bottom, nK0, nKp, nKm, p_tot);
 77        unsigned int nk = nKp-nKm+nK0;
 78        if (nk % 2 == 1) {
 79          p_tot -= pgamma;
 80          _h->fill(p_tot.mass()/GeV);
 81        }
 82      }
 83    }
 84
 85
 86    /// Normalise histograms etc., after the run
 87    void finalize() {
 88      scale(_h, 1e6/_nBottom->sumW());
 89    }
 90
 91    /// @}
 92
 93
 94    /// @name Histograms
 95    /// @{
 96    Histo1DPtr _h;
 97    CounterPtr _nBottom;
 98    /// @}
 99
100
101  };
102
103
104  RIVET_DECLARE_PLUGIN(BABAR_2012_I1122031);
105
106}