Rivet analyses

title: BELLE_2018_I1663447

Mass and angular distributions in $B^+\to K^+\eta\gamma$ decays

Experiment: BELLE (KEKB)

Inspire ID: 1663447

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 97 (2018) 9, 092003

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+, originally Upsilno(4S) decay

Mass and angular distributions in $B^+\to K^+\eta\gamma$ decays. Data were read from the plots in the paper, but are background subtracted and efficiency corrected.

Source code:BELLE_2018_I1663447.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B+ -> K+ eta gamma class BELLE_2018_I1663447 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2018_I1663447);


/// @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::ETA);
  declare(BP, "BP");
  for (unsigned int ix = 0; ix < 2; ++ix)
    for (unsigned int iy = 0; iy < 2; ++iy) book(_h[ix][iy], 1 + ix, 1, 1 + iy);
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{221, 1}, {321, 1}, {22, 1}};
  static const map<PdgId, unsigned int>& modeCC = {{221, 1}, {-321, 1}, {22, 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.decaying()[ix].pid() > 0 && BP.modeMatches(ix, 3, mode)) {
      sign = 1;
    }
    else if (BP.decaying()[ix].pid() < 0 && BP.modeMatches(ix, 3, modeCC)) {
      sign = -1;
    }
    else
      continue;
    const Particle& Kp = BP.decayProducts()[ix].at(sign * 321)[0];
    const Particle& eta = BP.decayProducts()[ix].at(221)[0];
    const Particle& gamma = BP.decayProducts()[ix].at(22)[0];
    FourMomentum pKeta = Kp.momentum() + eta.momentum();
    double mass = pKeta.mass();
    LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(
        BP.decaying()[ix].momentum().betaVec());
    pKeta = boostB.transform(pKeta);
    LorentzTransform boostKeta = LorentzTransform::mkFrameTransformFromBeta(pKeta.betaVec());
    FourMomentum pK = boostKeta.transform(boostB.transform(Kp.momentum()));
    FourMomentum pGamma = boostB.transform(gamma.momentum());
    double cTheta = pK.p3().unit().dot(pGamma.p3().unit());
    for (unsigned int iy = 0; iy < 2; ++iy) {
      _h[0][iy]->fill(cTheta);
      _h[1][iy]->fill(mass);
    }
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BELLE_2018_I1663447);

} ```