Rivet analyses

title: BESIII_2016_I1411645

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

Experiment: BESIII (BEPC)

Inspire ID: 1411645

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.D 94 (2016) 3, 032001

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+

Measurement of the kinematic distributions in $D^+\to K^-\pi^+ e^+\nu_e$ by BES-III. N.B. Although there is some data in HEPDATA it is not physical and therefore the data were read from the paper and may not have been corrected for acceptance.

Source code:BESIII_2016_I1411645.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 BESIII_2016_I1411645 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2016_I1411645);


/// @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 (unsigned int ix = 0; ix < 6; ++ix) book(_h[ix], 3, 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();
    _h[0]->fill(pKstar.mass());
    _h[1]->fill(pKstar.mass());
    FourMomentum qq = DP.decaying()[ix].momentum() - pKstar;
    _h[2]->fill(qq.mass2());
    // 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();
    _h[4]->fill(axisK.dot(pKstar.p3().unit()));
    LorentzTransform boostW = LorentzTransform::mkFrameTransformFromBeta(qq.betaVec());
    Vector3 axisE = boostW.transform(pe).p3().unit();
    _h[3]->fill(axisE.dot(qq.p3().unit()));
    axisK.setZ(0.);
    axisE.setZ(0.);
    double chi = atan2(axisE.cross(axisK).dot(qq.p3().unit()), axisE.dot(axisK));
    _h[5]->fill(chi);
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BESIII_2016_I1411645);

} ```