Rivet analyses

Kinematic distributions in D+ → K−π+e+νe

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+ → K−π+e+νe 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++ -*-
#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);

}