Rivet analyses

Kinematic distributions in D0 → π−π0e+νe

Experiment: BESIII (BEPC)

Inspire ID: 2825816

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 110 (2024) 11, 112018 - arXiv: 2409.04276

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0

Measurement of the kinematic distributions in D0 → π−π0e+νe by BES-III. N.B. the plots where read from the paper and may not have been corrected for acceptance.

Source code:BESIII_2024_I2825816.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/DecayedParticles.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief D0 -> pi pi semileptonic
  class BESIII_2024_I2825816 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2825816);


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

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

      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::pid == 421);
      declare(ufs, "UFS");
      DecayedParticles DD(ufs);
      DD.addStable(PID::PI0);
      DD.addStable(PID::K0S);
      DD.addStable(PID::ETA);
      DD.addStable(PID::ETAPRIME);
      declare(DD, "DD");
      // Book histograms
      for (unsigned int ix = 0; ix < 5; ++ix) book(_h[ix], 1, 1, 1 + ix);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{111, 1}, {-211, 1}, {-11, 1}, {12, 1}};
      DecayedParticles DD = apply<DecayedParticles>(event, "DD");
      // loop over particles
      for (unsigned int ix = 0; ix < DD.decaying().size(); ++ix) {
        if (!DD.modeMatches(ix, 4, mode)) continue;
        const Particle& pi0 = DD.decayProducts()[ix].at(111)[0];
        const Particle& pim = DD.decayProducts()[ix].at(-211)[0];
        const Particle& ep = DD.decayProducts()[ix].at(-11)[0];
        const Particle& nue = DD.decayProducts()[ix].at(12)[0];
        FourMomentum pRho = pi0.momentum() + pim.momentum();
        _h[0]->fill(pRho.mass());
        FourMomentum qq = DD.decaying()[ix].momentum() - pRho;
        _h[1]->fill(qq.mass2());
        // boost momenta to D rest frame
        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
            DD.decaying()[ix].momentum().betaVec());
        FourMomentum pPP = boost.transform(pRho);
        Matrix3 ptoz(-pPP.p3().unit(), Vector3(0, 0, 1));
        boost.preMult(ptoz);
        // the momenta in frane to W along z
        FourMomentum pD = boost.transform(DD.decaying()[ix].momentum());
        FourMomentum ppi0 = boost.transform(pi0.momentum());
        FourMomentum ppim = boost.transform(pim.momentum());
        FourMomentum pe = boost.transform(ep.momentum());
        FourMomentum pnu = boost.transform(nue.momentum());
        pRho = ppi0 + ppim;
        qq = pD - pRho;
        LorentzTransform boostRho = LorentzTransform::mkFrameTransformFromBeta(pRho.betaVec());
        Vector3 axisRho = boostRho.transform(ppim).p3().unit();
        _h[2]->fill(axisRho.dot(pRho.p3().unit()));
        LorentzTransform boostW = LorentzTransform::mkFrameTransformFromBeta(qq.betaVec());
        Vector3 axisE = boostW.transform(pe).p3().unit();
        _h[3]->fill(axisE.dot(qq.p3().unit()));
        axisRho.setZ(0.);
        axisE.setZ(0.);
        double chi = atan2(axisE.cross(axisRho).dot(qq.p3().unit()), axisE.dot(axisRho));
        _h[4]->fill(chi);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1., false);
    }

    /// @}


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


  RIVET_DECLARE_PLUGIN(BESIII_2024_I2825816);

}