Rivet analyses

title: BABAR_2008_I789278

Longitudinal polarization in $B^\pm\to\phi K^\pm_1$ and $\phi K^\pm_2$

Experiment: BABAR (PEP-II)

Inspire ID: 789278

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 101 (2008) 161801

Beams: * *

Beam energies: ANY

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

Measurement of the longitudinal polarization in $B^\pm\to\phi K^\pm_1$ and $\phi K^\pm_2$. The values were taken from Table I, due to the large backgrounds none of the distributions are implemented.

Source code:BABAR_2008_I789278.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B+ -> K_1+/K_2+ phixs class BABAR_2008_I789278 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2008_I789278);


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

/// Book histograms and initialise projections before the run
void init() {
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BP(ufs);
  BP.addStable(10323);
  BP.addStable(-10323);
  BP.addStable(325);
  BP.addStable(-325);
  BP.addStable(333);
  declare(BP, "BP");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_p[ix][0], 1, 1, 1 + ix);
    book(_p[ix][1], "TMP/wgt_" + toString(ix + 1));
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{333, 1}, {10323, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{333, 1}, {-10323, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{333, 1}, {325, 1}};
  static const map<PdgId, unsigned int>& mode2CC = {{333, 1}, {-325, 1}};

  DecayedParticles BP = apply<DecayedParticles>(event, "BP");
  // loop over particles
  for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
    int imode = -1;
    if (BP.modeMatches(ix, 2, mode1) || BP.modeMatches(ix, 2, mode1CC))
      imode = 0;
    else if (BP.modeMatches(ix, 2, mode2) || BP.modeMatches(ix, 2, mode2CC))
      imode = 1;
    else
      continue;
    // find phi decay products
    const Particle& phi = BP.decayProducts()[ix].at(333)[0];
    if (phi.children().size() != 2) continue;
    if (phi.children()[0].pid() != -phi.children()[1].pid()) continue;
    if (phi.children()[0].abspid() != 321) continue;
    Particle Kp = phi.children()[0].pid() > 0 ? phi.children()[0] : phi.children()[1];
    // boost to B rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
        BP.decaying()[ix].momentum().betaVec());
    FourMomentum pPhi = boost.transform(phi.momentum());
    FourMomentum pKp = boost.transform(Kp.momentum());
    const LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
    pKp = boost2.transform(pKp);
    double cK = pKp.p3().unit().dot(pPhi.p3().unit());
    _p[imode][0]->fill(-(1. - 5. * sqr(cK)) / 2.);
    _p[imode][1]->fill();
  }
}


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

/// @}


/// @name Histograms
/// @{
CounterPtr _p[2][2];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2008_I789278);

} ```