Rivet analyses

title: BABAR_2008_I792439

Mass and angular distributions in $B^0\to\phi K\pi$

Experiment: BABAR (PEP-II)

Inspire ID: 792439

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 78 (2008) 092008

Beams: * *

Beam energies: ANY

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

Measurment of mass and angular distributions in $B^0\to\phi K\pi$ decays. The corrected data were read from the figures in the paper.

Source code:BABAR_2008_I792439.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> phi K pi class BABAR_2008_I792439 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I792439);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511);
  declare(ufs, "UFS");
  DecayedParticles B0(ufs);
  B0.addStable(333);
  B0.addStable(310);
  B0.addStable(111);
  declare(B0, "B0");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_p[ix][0], 1, 2, 2 + ix);
    book(_p[ix][1], "TMP/norm_" + toString(ix));
    for (unsigned int iy = 0; iy < 2; ++iy) {
      book(_h_mass[ix][iy], 2, 1 + ix, 1 + iy);
      book(_h_angle[ix][iy], 3 + ix, 1, 1 + iy);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{321, 1}, {-211, 1}, {333, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{-321, 1}, {211, 1}, {333, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{310, 1}, {111, 1}, {333, 1}};
  DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
  // loop over particles
  for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
    int sign = 1, imode = -1;
    if (B0.modeMatches(ix, 3, mode1)) {
      imode = 0;
      sign = 1;
    }
    else if (B0.modeMatches(ix, 3, mode1CC)) {
      imode = 0;
      sign = -1;
    }
    else if (B0.modeMatches(ix, 3, mode2)) {
      imode = 1;
      sign = 1;
    }
    else
      continue;
    // particles
    const Particle& KK = B0.decayProducts()[ix].at(imode == 0 ? 321 * sign : 310)[0];
    const Particle& pi = B0.decayProducts()[ix].at(imode == 0 ? -211 * sign : 111)[0];
    const Particle& phi = B0.decayProducts()[ix].at(333)[0];
    // children of the phi
    if (phi.children().size() != 2) continue;
    if (phi.children()[0].abspid() != 321) continue;
    if (phi.children()[0].pid() != -phi.children()[1].pid()) continue;
    double mKpi = (KK.momentum() + pi.momentum()).mass();
    _h_mass[imode][0]->fill(mKpi);
    _h_mass[imode][1]->fill(phi.mass());
    Particle Kp1 = phi.children()[0];
    Particle Km1 = phi.children()[1];
    // B0 frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
        B0.decaying()[ix].momentum().betaVec());
    FourMomentum pKstar = boost1.transform(KK.momentum() + pi.momentum());
    FourMomentum pPhi = boost1.transform(phi.momentum());
    // K pi helicity angle
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
    FourMomentum pKp = boost2.transform(boost1.transform(KK.momentum()));
    Vector3 axis1 = pKstar.p3().unit();
    double cTheta1 = axis1.dot(pKp.p3().unit());
    // phi helicity angle
    LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
    FourMomentum pKp1 = boost3.transform(boost1.transform(Kp1.momentum()));
    Vector3 axis2 = pPhi.p3().unit();
    double cTheta2 = axis2.dot(pKp1.p3().unit());
    if (mKpi > .75 && mKpi < 1.05) {
      _h_angle[0][0]->fill(cTheta1);
      _h_angle[0][1]->fill(cTheta2);
      _p[0][0]->fill(-0.5 * (1 - 5. * sqr(cTheta2)));
      _p[0][1]->fill();
    }
    else if (mKpi > 1.13 && mKpi < 1.53) {
      _h_angle[1][0]->fill(cTheta1);
      _h_angle[1][1]->fill(cTheta2);
      _p[1][0]->fill(-0.5 * (1 - 5. * sqr(cTheta2)));
      _p[1][1]->fill();
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_mass[2][2], _h_angle[2][2];
CounterPtr _p[2][2];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2008_I792439);

} ```