Rivet analyses

title: BABAR_2010_I879997

Kinematic distributions in $D^+\to K^-\pi^+ e^+\nu_e$

Experiment: BABAR (PEP-II)

Inspire ID: 879997

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 83 (2011) 072001

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+

Measurement of the kinematic distributions in $D^+\to K^-\pi^+ e^+\nu_e$ by BABAR. The data were read from the paper and may not have been corrected for acceptance. In many cases the error bar is the size of the point

Source code:BABAR_2010_I879997.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D+ -> K- pi+ e+ nu_e class BABAR_2010_I879997 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2010_I879997);


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

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 411);
  declare(ufs, "UFS");
  DecayedParticles DP(ufs);
  DP.addStable(PID::PI0);
  DP.addStable(PID::K0S);
  DP.addStable(PID::ETA);
  DP.addStable(PID::ETAPRIME);
  declare(DP, "DP");

  // Book histograms
  for (size_t ix = 0; ix < 5; ++ix) {
    book(_h[ix], 1, 1, 1 + ix);
  }
  const vector<double> bins{0., 0.8, 0.9, 1., 1.6};
  for (size_t ix = 0; ix < 4; ++ix) {
    book(_b[ix], bins);
    for (auto& b : _b[ix]->bins()) {
      book(b, 1 + b.index(), 1, 1 + ix);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode = {{-321, 1}, {211, 1}, {-11, 1}, {12, 1}};
  DecayedParticles DP = apply<DecayedParticles>(event, "DP");
  // loop over particles
  for (unsigned int ix = 0; ix < DP.decaying().size(); ++ix) {
    if (!DP.modeMatches(ix, 4, mode)) continue;
    const Particle& Km = DP.decayProducts()[ix].at(-321)[0];
    const Particle& pip = DP.decayProducts()[ix].at(211)[0];
    const Particle& ep = DP.decayProducts()[ix].at(-11)[0];
    const Particle& nue = DP.decayProducts()[ix].at(12)[0];
    FourMomentum pKstar = Km.momentum() + pip.momentum();
    double mKpi = pKstar.mass();
    _h[4]->fill(mKpi);
    FourMomentum qq = DP.decaying()[ix].momentum() - pKstar;
    double q2 = qq.mass2();
    _h[0]->fill(q2);
    _b[0]->fill(mKpi, q2);
    // boost momenta to DP rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
        DP.decaying()[ix].momentum().betaVec());
    FourMomentum pKS = boost.transform(pKstar);
    Matrix3 ptoz(-pKS.p3().unit(), Vector3(0, 0, 1));
    boost.preMult(ptoz);
    // the momenta in frane to W along z
    FourMomentum pD = boost.transform(DP.decaying()[ix].momentum());
    FourMomentum pK = boost.transform(Km.momentum());
    FourMomentum ppi = boost.transform(pip.momentum());
    FourMomentum pe = boost.transform(ep.momentum());
    FourMomentum pnu = boost.transform(nue.momentum());
    pKstar = pK + ppi;
    qq = pD - pKstar;
    LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
    Vector3 axisK = boostK.transform(pK).p3().unit();
    double cosK = axisK.dot(pKstar.p3().unit());
    _h[2]->fill(cosK);
    _b[2]->fill(mKpi, cosK);
    LorentzTransform boostW = LorentzTransform::mkFrameTransformFromBeta(qq.betaVec());
    Vector3 axisE = boostW.transform(pe).p3().unit();
    double cosE = axisE.dot(qq.p3().unit());
    _h[3]->fill(cosE);
    _b[3]->fill(mKpi, cosE);
    axisK.setZ(0.);
    axisE.setZ(0.);
    double chi = atan2(axisE.cross(axisK).dot(qq.p3().unit()), axisE.dot(axisK));
    _h[1]->fill(chi);
    _b[1]->fill(mKpi, chi);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[5];
Histo1DGroupPtr _b[4];
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2010_I879997);

} ```