Rivet analyses

title: BELLE_2006_I735859

Helicity angle in $B\to\omega K$ and $B^+\to\omega\pi^+$

Experiment: BELLE (KEKB)

Inspire ID: 735859

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 74 (2006) 111101

Beams: * *

Beam energies: ANY

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

Measurement of the helicty angle in $B\to\omega K$ and $B^+\to\omega\pi^+$ decays. The data were read from Figure2 in the paper and are background subtracted. The mass distributions are not implemented due to resolution effects.

Source code:BELLE_2006_I735859.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> omega pi/K class BELLE_2006_I735859 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2006_I735859);


/// @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(310);
  BB.addStable(223);
  declare(BB, "BB");
  // histos
  for (unsigned int ix = 0; ix < 3; ++ix) {
    book(_h[ix], 1, 1, 1 + ix);
  }
}

void findChildren(const Particle& p,
                  Particles& pim,
                  Particles& pip,
                  Particles& pi0,
                  unsigned int& ncount) {
  for (const Particle& child : p.children()) {
    if (child.pid() == PID::PIPLUS) {
      pip.push_back(child);
      ncount += 1;
    }
    else if (child.pid() == PID::PIMINUS) {
      pim.push_back(child);
      ncount += 1;
    }
    else if (child.pid() == PID::PI0) {
      pi0.push_back(child);
      ncount += 1;
    }
    else if (child.children().empty()) {
      ncount += 1;
    }
    else {
      findChildren(child, pim, pip, pi0, ncount);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles BB = apply<DecayedParticles>(event, "BB");
  // loop over particles
  for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
    unsigned int imode = 0;
    if (BB.modeMatches(ix, 2, mode1) || BB.modeMatches(ix, 2, mode1CC)) {
      imode = 0;
    }
    else if (BB.modeMatches(ix, 2, mode2) || BB.modeMatches(ix, 2, mode2CC)) {
      imode = 1;
    }
    else if (BB.modeMatches(ix, 2, mode3) || BB.modeMatches(ix, 2, mode3CC)) {
      imode = 2;
    }
    else {
      continue;
    }
    const Particle& omega = BB.decayProducts()[ix].at(223)[0];
    // children of the omega
    unsigned int ncount = 0;
    Particles pip, pim, pi0;
    findChildren(omega, pim, pip, pi0, ncount);
    if (ncount != 3 || !(pim.size() == 1 && pip.size() == 1 && pi0.size() == 1)) continue;
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        BB.decaying()[ix].mom().betaVec());
    FourMomentum pomega = boost1.transform(omega.mom());
    FourMomentum pPip = boost1.transform(pip[0].mom());
    FourMomentum pPim = boost1.transform(pim[0].mom());
    // boost to omega frame
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pomega.betaVec());
    pPip = boost3.transform(pPip);
    pPim = boost3.transform(pPim);
    Vector3 axisOmega = pPip.p3().cross(pPim.p3()).unit();
    // helicity angle
    _h[imode]->fill(abs(pomega.p3().unit().dot(axisOmega)));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h, 1.0, false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[3];
const map<PdgId, unsigned int> mode1 = {{223, 1}, {321, 1}};
const map<PdgId, unsigned int> mode1CC = {{223, 1}, {-321, 1}};
const map<PdgId, unsigned int> mode2 = {{223, 1}, {211, 1}};
const map<PdgId, unsigned int> mode2CC = {{223, 1}, {-211, 1}};
const map<PdgId, unsigned int> mode3 = {{223, 1}, {130, 1}};
const map<PdgId, unsigned int> mode3CC = {{223, 1}, {310, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2006_I735859);

} ```