Rivet analyses

title: BESIII_2023_I2674768

Kinematic distributions in $D^+s\to K^+K^- \mu^+\nu\mu$

Experiment: BESIII (BEPC)

Inspire ID: 2674768

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2307.03024

Beams: * *

Beam energies: ANY

Run details: - Any process producing Ds mesons

Measurement of the kinematic distributions in $D^+s\to K^+K^- \mu^+\nu\mu$ by BESIII. N.B. the plots where read from the paper and may not have been corrected for acceptance.

Source code:BESIII_2023_I2674768.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D_s+ -> K+K- mu+ nu_mu class BESIII_2023_I2674768 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2023_I2674768);


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

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

  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 431);
  declare(ufs, "UFS");
  DecayedParticles DS(ufs);
  DS.addStable(PID::PI0);
  DS.addStable(PID::K0S);
  DS.addStable(PID::ETA);
  DS.addStable(PID::ETAPRIME);
  declare(DS, "DS");
  // 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) {
  DecayedParticles DS = apply<DecayedParticles>(event, "DS");
  // loop over particles
  for (unsigned int ix = 0; ix < DS.decaying().size(); ++ix) {
    if (!DS.modeMatches(ix, 4, mode)) continue;
    const Particle& Kp = DS.decayProducts()[ix].at(321)[0];
    const Particle& Km = DS.decayProducts()[ix].at(-321)[0];
    const Particle& ep = DS.decayProducts()[ix].at(-13)[0];
    const Particle& nue = DS.decayProducts()[ix].at(14)[0];
    FourMomentum pPhi = Kp.mom() + Km.mom();
    _h[0]->fill(pPhi.mass());
    FourMomentum qq = DS.decaying()[ix].mom() - pPhi;
    _h[1]->fill(qq.mass2());
    // boost momenta to DS rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
        DS.decaying()[ix].mom().betaVec());
    FourMomentum pPHI = boost.transform(pPhi);
    Matrix3 ptoz(-pPHI.p3().unit(), Vector3(0, 0, 1));
    boost.preMult(ptoz);
    // the momenta in frane to W along z
    FourMomentum pD = boost.transform(DS.decaying()[ix].mom());
    FourMomentum pKp = boost.transform(Kp.mom());
    FourMomentum pKm = boost.transform(Km.mom());
    FourMomentum pe = boost.transform(ep.mom());
    FourMomentum pnu = boost.transform(nue.mom());
    pPhi = pKp + pKm;
    qq = pD - pPhi;
    LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pPhi.betaVec());
    Vector3 axisK = boostK.transform(pKp).p3().unit();
    _h[2]->fill(axisK.dot(pPhi.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.);
    const double chi = atan2(axisE.cross(axisK).dot(qq.p3().unit()), axisE.dot(axisK));
    _h[4]->fill(chi);
  }
}


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

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[5];
const map<PdgId, unsigned int> mode = {{321, 1}, {-321, 1}, {-13, 1}, {14, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2023_I2674768);

} ```