Rivet analyses

D⁺ → η^′ℓ⁺ν_ℓ

Experiment: BESIII ()

Inspire ID: 2839350

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 134 (2025) 11, 111801 - arXiv: 2410.08603

Beams: * *

Beam energies: ANY

Run details: - Any process producing D+

Measurement of the q² spectrum in the decay D⁺ → η^′ℓ⁺ν_ℓ BES-III.

Source code:`BESIII_2024_I2839350.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief D+ -> eta' ell nu
  class BESIII_2024_I2839350 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BESIII_2024_I2839350);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(UnstableParticles(Cuts::abspid == 411), "UFS");

      for (unsigned int ix = 0; ix < 2; ++ix)
        book(_h[ix], "TMP/h_" + toString(ix + 1), refData(1, 1, 1 + ix));
      book(_c, "TMP/c_Dplus");
    }

    // 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()) {
        // remove particles from radiation/mixing
        bool self = false;
        for (const Particle& child : p.children()) self |= p.abspid() == child.pid();
        if (self) continue;
        _c->fill();
        if (isSemileptonicDecay(p, {PID::ETAPRIME, PID::EPLUS, PID::NU_E})) {
          _h[1]->fill(q2(p, PID::ETAPRIME));
        }
        else if (isSemileptonicDecay(p, {PID::ETAPRIME, PID::ANTIMUON, PID::NU_MU})) {
          _h[0]->fill(q2(p, PID::ETAPRIME));
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      double tau = 1033e-6;
      for (unsigned int ix = 0; ix < 2; ++ix) {
        Estimate1DPtr tmp;
        book(tmp, 1, 1, 1 + ix);
        barchart(_h[ix], tmp);
        scale(tmp, 1. / tau / *_c);
      }
    }

    /// @}


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


  RIVET_DECLARE_PLUGIN(BESIII_2024_I2839350);

}

Rivet analyses

D+ → η′ℓ+νℓ

Source code:BESIII_2024_I2839350.cc

D⁺ → η^′ℓ⁺ν_ℓ

Source code:`BESIII_2024_I2839350.cc`