Rivet analyses

title: BESIII_2024_I2819140

Exclusive $D^0\to K^-\ell^+\nu_\ell$ and $D^+\to \bar{K}^0\ell^+\nu_\ell$ decays

Experiment: BESIII (BEPC)

Inspire ID: 2819140

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2408.09087

Beams: * *

Beam energies: ANY

Run details: - Events with D-decays, either particle guns or collisions.

Differential decay rates for semi-leptonic $D^0\to K^-\ell^+\nu_\ell$ and $D^+\to \bar{K}^0\ell^+\nu_\ell$ decays

Source code:BESIII_2024_I2819140.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D0 -> K- ell+ nu_ell and D+ -> Kbar0 ell+ nu_ell class BESIII_2024_I2819140 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2819140);


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

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

  // Initialise and register projections
  declare(UnstableParticles(Cuts::abspid == 411 || Cuts::abspid == 421), "UFS");

  for (unsigned int ix = 0; ix < 4; ++ix) {
    book(_h[ix], 1 + ix, 1, 1);
    if (ix > 1) continue;
    book(_c[ix], "TMP/c_" + toString(ix + 1));
  }
}

// Calculate the Q2 using mother and daugher meson
double q2(const Particle& B, int mesonID) {
  FourMomentum q = B.mom() - select(B.children(), Cuts::pid == 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 (p.pid() == 421) {
      _c[0]->fill();
      if (isSemileptonicDecay(p, {PID::KMINUS, PID::EPLUS, PID::NU_E})) {
        _h[0]->fill(q2(p, PID::KMINUS));
      }
      else if (isSemileptonicDecay(p, {PID::KMINUS, PID::ANTIMUON, PID::NU_MU})) {
        _h[1]->fill(q2(p, PID::KMINUS));
      }
    }
    else if (p.pid() == -421) {
      _c[0]->fill();
      if (isSemileptonicDecay(p, {PID::KPLUS, PID::EMINUS, PID::NU_EBAR})) {
        _h[0]->fill(q2(p, PID::KPLUS));
      }
      else if (isSemileptonicDecay(p, {PID::KPLUS, PID::MUON, PID::NU_MUBAR})) {
        _h[1]->fill(q2(p, PID::KPLUS));
      }
    }
    else if (p.pid() == 411) {
      _c[1]->fill();
      if (isSemileptonicDecay(p, {-311, PID::EPLUS, PID::NU_E})) {
        _h[2]->fill(q2(p, -311));
      }
      else if (isSemileptonicDecay(p, {-311, PID::ANTIMUON, PID::NU_MU})) {
        _h[3]->fill(q2(p, -311));
      }
      else if (isSemileptonicDecay(p, {130, PID::EPLUS, PID::NU_E})) {
        _h[2]->fill(q2(p, 130));
      }
      else if (isSemileptonicDecay(p, {130, PID::ANTIMUON, PID::NU_MU})) {
        _h[3]->fill(q2(p, 130));
      }
      else if (isSemileptonicDecay(p, {310, PID::EPLUS, PID::NU_E})) {
        _h[2]->fill(q2(p, 310));
      }
      else if (isSemileptonicDecay(p, {310, PID::ANTIMUON, PID::NU_MU})) {
        _h[3]->fill(q2(p, 310));
      }
    }
    else if (p.pid() == -411) {
      _c[1]->fill();
      if (isSemileptonicDecay(p, {311, PID::EMINUS, PID::NU_EBAR})) {
        _h[2]->fill(q2(p, 311));
      }
      else if (isSemileptonicDecay(p, {311, PID::MUON, PID::NU_MUBAR})) {
        _h[3]->fill(q2(p, 311));
      }
      else if (isSemileptonicDecay(p, {130, PID::EMINUS, PID::NU_EBAR})) {
        _h[2]->fill(q2(p, 130));
      }
      else if (isSemileptonicDecay(p, {130, PID::MUON, PID::NU_MUBAR})) {
        _h[3]->fill(q2(p, 130));
      }
      else if (isSemileptonicDecay(p, {310, PID::EMINUS, PID::NU_EBAR})) {
        _h[2]->fill(q2(p, 310));
      }
      else if (isSemileptonicDecay(p, {310, PID::MUON, PID::NU_MUBAR})) {
        _h[3]->fill(q2(p, 310));
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // lifetimes from PDG 2022 [ns] (as in paper)
  double tau[2] = {410.3e-6, 1033e-6};
  for (unsigned int ix = 0; ix < 4; ++ix) scale(_h[ix], 1. / tau[ix / 2] / *_c[ix / 2]);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[4];
CounterPtr _c[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BESIII_2024_I2819140);

} ```