Rivet analyses

title: BABAR_2011_I901433

Angular distributions in $B\to\phi\phi K$ decays

Experiment: BABAR (PEP-II)

Inspire ID: 901433

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 84 (2011) 012001

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+ and B0 mesons, originally Upsilon(4S) decays

Measurement of angular distributions in $B\to\phi\phi K$ decays for $m_{\phi\phi}$ both in the region of the $\eta_c$ resonance and below this region.

Source code:BABAR_2011_I901433.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> phi phi K class BABAR_2011_I901433 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2011_I901433);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 or Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BB(ufs);
  BB.addStable(PID::PHI);
  BB.addStable(PID::K0S);
  declare(BB, "BB");
  // histograms
  for (unsigned int ix = 0; ix < 6; ++ix) book(_h[ix], 1, 1, 1 + ix);
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles BB = apply<DecayedParticles>(event, "BB");
  static const map<PdgId, unsigned int>& mode1 = {{333, 2}, {321, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{333, 2}, {-321, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{333, 2}, {310, 1}};
  for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
    if (BB.modeMatches(ix, 3, mode1) || BB.modeMatches(ix, 3, mode1CC) || BB.modeMatches(ix, 3, mode2)) {
      // phi mesons
      const Particles& phi = BB.decayProducts()[ix].at(333);
      // bost to B rest frane
      LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(
          BB.decaying()[ix].momentum().betaVec());
      FourMomentum pPhiPhi = boost1.transform(phi[0].momentum() + phi[1].momentum());
      double mPhiPhi = pPhiPhi.mass();
      int iloc = -1;
      if (mPhiPhi > 2.94 && mPhiPhi < 3.02)
        iloc = 0;
      else if (mPhiPhi < 2.85)
        iloc = 3;
      else
        continue;
      // cos theta phi phi
      Vector3 axis1 = pPhiPhi.p3().unit();
      LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pPhiPhi.betaVec());
      Vector3 axis2 = boost2.transform(boost1.transform(phi[0].momentum())).p3().unit();
      _h[iloc + 2]->fill(abs(axis1.dot(axis2)));
      // now for the phi decays
      Vector3 Trans[2];
      bool foundPhi = true;
      for (unsigned int ix = 0; ix < 2; ++ix) {
        if (phi[ix].children().size() != 2 || phi[ix].children()[0].pid() != -phi[ix].children()[1].pid()
            || phi[ix].children()[0].abspid() != 321) {
          foundPhi = false;
          break;
        }
        Particle Km = phi[ix].children()[0];
        Particle Kp = phi[ix].children()[1];
        if (Kp.pid() < 0) swap(Km, Kp);
        FourMomentum pKp = boost2.transform(boost1.transform(Kp.momentum()));
        FourMomentum pPhi = boost2.transform(boost1.transform(phi[ix].momentum()));
        LorentzTransform boost3 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
        pKp = boost3.transform(pKp);
        double cK = axis2.dot(pKp.p3().unit());
        _h[iloc + 1]->fill(cK);
        Trans[ix] = pKp.p3() - cK * pKp.p3().mod() * axis2;
      }
      if (!foundPhi) continue;
      double chi = atan2(Trans[0].cross(Trans[1]).dot(axis2), Trans[0].dot(Trans[1]));
      _h[iloc]->fill(abs(chi));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 6; ++ix) normalize(_h[ix], 1., false);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[6];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2011_I901433);

} ```