Rivet analyses

title: BABAR_2009_I785439

Mass distributions in $B\to\eta K\gamma$ decays

Experiment: BABAR (PEP-II)

Inspire ID: 785439

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 79 (2009) 011102

Beams: * *

Beam energies: ANY

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

Mass distributions in $B\to\eta K\gamma$ decays

Source code:BABAR_2009_I785439.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> eta K gamma class BABAR_2009_I785439 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I785439);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BB(ufs);
  BB.addStable(PID::ETA);
  BB.addStable(PID::K0S);
  declare(BB, "BB");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) book(_h[ix], 1, 1, 1 + ix);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{221, 1}, {310, 1}, {22, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{221, 1}, {321, 1}, {22, 1}};
  static const map<PdgId, unsigned int>& mode2CC = {{221, 1}, {-321, 1}, {22, 1}};
  DecayedParticles BB = apply<DecayedParticles>(event, "BB");
  // loop over particles
  for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
    int imode = 0, sign = 1;
    if (BB.decaying()[ix].abspid() == 511) {
      imode = 1;
      if (!BB.modeMatches(ix, 3, mode1)) continue;
    }
    else {
      imode = 0;
      if (BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode2)) {
        sign = 1;
      }
      else if (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode2CC)) {
        sign = -1;
      }
      else
        continue;
    }
    const Particle& KK = BB.decayProducts()[ix].at(imode == 0 ? sign * 321 : 310)[0];
    const Particle& eta = BB.decayProducts()[ix].at(221)[0];
    _h[imode]->fill((KK.momentum() + eta.momentum()).mass());
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2009_I785439);

} ```