Rivet analyses

title: CLEOC_2008_I769777

$q^2$ spectra in semi-leptonic $D$ decays

Experiment: CLEOC (CESR)

Inspire ID: 769777

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev. D77 (2008) 112005

Beams: * *

Beam energies: ANY

Run details: - any process producing charm mesons

Measurement of the $q^2$ spectra for semi-leptonic $D$ meson decays by CLEOC.

Source code:CLEOC_2008_I769777.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D -> pi,K semi-leptonic q^2 class CLEOC_2008_I769777 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOC_2008_I769777);


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

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

  // Initialise and register projections
  declare(UnstableParticles(), "UFS");
  // histograms
  book(_h_q2_D0_pi, 1, 1, 1);
  book(_h_q2_Dp_pi, 1, 1, 2);
  book(_h_q2_D0_K, 1, 1, 3);
  book(_h_q2_Dp_K, 1, 1, 4);
  book(_nD0, "TMP/nD0");
  book(_nDp, "TMP/nDp");
}

// Calculate the Q2 using mother and daugher meson
double q2(const Particle& B, int mesonID) {
  FourMomentum q = B.mom() - select(B.children(), Cuts::abspid == abs(mesonID))[0];
  return q * q;
}

// Check for explicit decay into pdgids
bool isSemileptonicDecay(const Particle& mother, vector<int> ids) {
  // Trivial check to ignore any other decays but the one in question modulo photons
  const Particles children = mother.children(Cuts::pid != PID::PHOTON);
  if (children.size() != ids.size()) return false;
  // Check for the explicit decay
  return all(ids, [&](int i) { return count(children, hasPID(i)) == 1; });
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // Loop over D mesons
  for (const Particle& p : apply<UnstableParticles>(event, "UFS")
                               .particles(Cuts::abspid == PID::D0 or Cuts::abspid == PID::DPLUS)) {
    if (p.abspid() == PID::D0) {
      _nD0->fill();
      if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E})
          || isSemileptonicDecay(p, {PID::PIPLUS, PID::ELECTRON, PID::NU_EBAR}))
        _h_q2_D0_pi->fill(q2(p, PID::PIMINUS));
      else if (isSemileptonicDecay(p, {PID::KMINUS, PID::POSITRON, PID::NU_E})
               || isSemileptonicDecay(p, {PID::KPLUS, PID::ELECTRON, PID::NU_EBAR}))
        _h_q2_D0_K->fill(q2(p, PID::KMINUS));
    }
    else if (p.abspid() == PID::DPLUS) {
      _nDp->fill();
      if (isSemileptonicDecay(p, {PID::PI0, PID::POSITRON, PID::NU_E})
          || isSemileptonicDecay(p, {PID::PI0, PID::ELECTRON, PID::NU_EBAR}))
        _h_q2_Dp_pi->fill(q2(p, PID::PI0));
      else if (isSemileptonicDecay(p, {-311, PID::POSITRON, PID::NU_E}))
        _h_q2_Dp_K->fill(q2(p, -311));
      else if (isSemileptonicDecay(p, {311, PID::ELECTRON, PID::NU_EBAR}))
        _h_q2_Dp_K->fill(q2(p, 311));
      else if (isSemileptonicDecay(p, {PID::K0S, PID::POSITRON, PID::NU_E})
               || isSemileptonicDecay(p, {PID::K0S, PID::ELECTRON, PID::NU_EBAR}))
        _h_q2_Dp_K->fill(q2(p, PID::K0S));
      else if (isSemileptonicDecay(p, {PID::K0L, PID::POSITRON, PID::NU_E})
               || isSemileptonicDecay(p, {PID::K0L, PID::ELECTRON, PID::NU_EBAR}))
        _h_q2_Dp_K->fill(q2(p, PID::K0L));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_q2_D0_pi, 100. / *_nD0);
  scale(_h_q2_D0_K, 100. / *_nD0);
  scale(_h_q2_Dp_pi, 100. / *_nDp);
  scale(_h_q2_Dp_K, 100. / *_nDp);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_q2_D0_pi, _h_q2_D0_K, _h_q2_Dp_pi, _h_q2_Dp_K;
CounterPtr _nD0, _nDp;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOC_2008_I769777);

} ```