Rivet analyses

title: BELLE_2013_I1238273

Exclusive semileptonic B-decays

Experiment: BELLE (KEKB)

Inspire ID: 1238273

Status: VALIDATED

Authors: - Holger Schulz

References: none listed

Beams: * *

Beam energies: ANY

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

Implementation of Lorentz invariant q2 distributions ("form factor") for semileptonic B decays

Source code:BELLE_2013_I1238273.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Add a short analysis description here class BELLE_2013_I1238273 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1238273);


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

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

  // Initialise and register projections
  declare(UnstableParticles(), "UFS");

  // Book histograms
  book(_h_q2_B0bar_pi, 1, 1, 1);
  book(_h_q2_B0bar_rho, 3, 1, 1);
  book(_h_q2_Bminus_pi, 2, 1, 1);
  book(_h_q2_Bminus_rho, 4, 1, 1);
  book(_h_q2_Bminus_omega, 5, 1, 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 B0bar Mesons
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid == PID::B0BAR)) {
    if (isSemileptonicDecay(p, {PID::PIPLUS, PID::ELECTRON, PID::NU_EBAR})
        || isSemileptonicDecay(p, {PID::PIPLUS, PID::MUON, PID::NU_MUBAR})) {
      _h_q2_B0bar_pi->fill(q2(p, PID::PIPLUS));
    }
    if (isSemileptonicDecay(p, {PID::RHOPLUS, PID::ELECTRON, PID::NU_EBAR})
        || isSemileptonicDecay(p, {PID::RHOPLUS, PID::MUON, PID::NU_MUBAR})) {
      _h_q2_B0bar_rho->fill(q2(p, PID::RHOPLUS));
    }
  }
  // Loop over B- Mesons
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::pid == PID::BMINUS)) {
    if (isSemileptonicDecay(p, {PID::PI0, PID::ELECTRON, PID::NU_EBAR})
        || isSemileptonicDecay(p, {PID::PI0, PID::MUON, PID::NU_MUBAR})) {
      _h_q2_Bminus_pi->fill(q2(p, PID::PI0));
    }
    if (isSemileptonicDecay(p, {PID::RHO0, PID::ELECTRON, PID::NU_EBAR})
        || isSemileptonicDecay(p, {PID::RHO0, PID::MUON, PID::NU_MUBAR})) {
      _h_q2_Bminus_rho->fill(q2(p, PID::RHO0));
    }
    if (isSemileptonicDecay(p, {PID::OMEGA, PID::ELECTRON, PID::NU_EBAR})
        || isSemileptonicDecay(p, {PID::OMEGA, PID::MUON, PID::NU_MUBAR})) {
      _h_q2_Bminus_omega->fill(q2(p, PID::OMEGA));
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {

  normalize(_h_q2_B0bar_pi, 298.8);     // normalize to BF*dQ2
  normalize(_h_q2_B0bar_rho, 1304.8);   // normalize to BF*dQ2
  normalize(_h_q2_Bminus_pi, 324.8);    // normalize to BF*dQ2
  normalize(_h_q2_Bminus_rho, 367.0);   // normalize to BF*dQ2
  normalize(_h_q2_Bminus_omega, 793.1); // normalize to BF*dQ2
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DPtr _h_q2_B0bar_pi;
Histo1DPtr _h_q2_B0bar_rho;
Histo1DPtr _h_q2_Bminus_pi;
Histo1DPtr _h_q2_Bminus_rho;
Histo1DPtr _h_q2_Bminus_omega;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2013_I1238273);

} ```