Rivet analyses

title: BELLE_2006_I715430

Form factors in $D^0\to(\pi^-,K^-)\ell^+\nu_\ell$

Experiment: BELLE (KEKB)

Inspire ID: 715430

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 97 (2006) 061804

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0 mesons, originally Upsilon(4S)

Measurement of the form factors in $D^0\to(\pi^-,K^-)\ell^+\nu_\ell$. The corrected data was read from the figure 2 in the paper.

Source code:BELLE_2006_I715430.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D0 -> pi, K ell nu_ell class BELLE_2006_I715430 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2006_I715430);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(Cuts::abspid == PID::D0), "UFS");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h[ix], "TMP/h_" + toString(ix + 1), refData(1 + ix, 1, 1));
  }
  book(_c, "TMP/nD");
}

// Calculate the Q2 using mother and daugher meson
double q2(const Particle& B, int mesonID) const {
  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) const {
  // 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) {
  const double M0 = 1.86484, M02 = sqr(M0);
  const double m2[2] = {sqr(0.493677), sqr(0.13957039)};
  // Loop over D mesons
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    _c->fill();
    if (isSemileptonicDecay(p, {PID::PIMINUS, PID::POSITRON, PID::NU_E})
        || isSemileptonicDecay(p, {PID::PIPLUS, PID::ELECTRON, PID::NU_EBAR})) {
      double qq = q2(p, PID::PIMINUS);
      double pcm = sqrt(
          0.25 / M02
          * (sqr(M02) + sqr(qq) + sqr(m2[1]) - 2. * qq * m2[1] - 2. * M02 * qq - 2. * m2[1] * M02));
      _h[1]->fill(qq, 1. / pow(pcm, 3));
    }
    else if (isSemileptonicDecay(p, {PID::KMINUS, PID::POSITRON, PID::NU_E})
             || isSemileptonicDecay(p, {PID::KPLUS, PID::ELECTRON, PID::NU_EBAR})) {
      double qq = q2(p, PID::KMINUS);
      double pcm = sqrt(
          0.25 / M02
          * (sqr(M02) + sqr(qq) + sqr(m2[0]) - 2. * qq * m2[0] - 2. * M02 * qq - 2. * m2[0] * M02));
      _h[0]->fill(qq, 1. / pow(pcm, 3));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  const double GF = 1.1663788e-5;
  const double CKM[2] = {0.975, 0.221};
  const double gamma = 6.582119569e-25 / 4.103e-13;
  const double pre = 24. * pow(M_PI, 3) / sqr(GF) * gamma;
  for (unsigned int ix = 0; ix < 2; ++ix) {
    double fact = pre / sqr(CKM[ix]);
    Estimate1DPtr tmp;
    book(tmp, 1 + ix, 1, 1);
    scale(_h[ix], fact / *_c);
    for (unsigned int iy = 0; iy < _h[ix]->numBins(); ++iy) {
      double val = _h[ix]->bin(iy + 1).sumW() / _h[ix]->bin(iy + 1).xWidth();
      double err = _h[ix]->bin(iy + 1).errW() / _h[ix]->bin(iy + 1).xWidth();
      val = sqrt(val);
      err /= 2. * val;
      tmp->bin(iy + 1).set(val, err);
    }
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[2];
CounterPtr _c;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2006_I715430);

} ```