Rivet analyses

title: CLEO_2004_I654843

$q^2$ spectra in $D^0\to (\pi^-,K^-) e^+\nu_e$

Experiment: CLEO (CESR)

Inspire ID: 654843

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 94 (2005) 011802

Beams: * *

Beam energies: ANY

Run details: - any process producing charm mesons

Measurement of the $q^2$ spectra for semi-leptonic $D_0$ meson decays by CLEO.

Source code:CLEO_2004_I654843.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D -> pi,K semi-leptonic q^2 class CLEO_2004_I654843 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_2004_I654843);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(Cuts::abspid == PID::D0), "UFS");
  // histograms
  book(_h_q2_D0_K, 1, 1, 1);
  book(_h_q2_D0_pi, 1, 1, 2);
}

// 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()) {
    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));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_q2_D0_K);
  normalize(_h_q2_D0_pi);
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(CLEO_2004_I654843);

} ```