Rivet analyses

title: CLEO_1997_I443704

Exclusive semileptonic $B$ to $D$ decays.

Experiment: CLEO (CESR)

Inspire ID: 443704

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 79 (1997) 2208-2212

Beams: * *

Beam energies: ANY

Run details: - Any process producing B mesons, originally Upslion(4S) decay

Measurement of the differential partial width with respect to $w$ for $B$ to $D$ semi-leptonic decays.

Source code:CLEO_1997_I443704.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> D semileptonic class CLEO_1997_I443704 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEO_1997_I443704);


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

/// Book histograms and initialise projections before the run
void init() {
  // projection
  declare(UnstableParticles(Cuts::pid == 511 || Cuts::pid == 521), "UFS");
  // histograms
  book(_h, 1, 1, 1);
  book(_c, "TMP/nB");
}

// 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; });
}

// Calculate the recoil w using mother and daugher meson
double recoilW(const Particle& B, int mesonID) {
  // TODO why does that not work with const?
  Particle D = select(B.children(), Cuts::pid == mesonID)[0];
  FourMomentum q = B.mom() - D.mom();
  return (B.mom() * B.mom() + D.mom() * D.mom() - q * q)
      / (2. * sqrt(B.mom() * B.mom()) * sqrt(D.mom() * D.mom()));
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  const double tau[2] = {1.519e-3, 1.638e-3};
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    if (p.children().size() <= 1) continue;
    if (p.pid() == PID::BPLUS) {
      _c->fill();
      if (isSemileptonicDecay(p, {PID::D0BAR, PID::POSITRON, PID::NU_E}))
        _h->fill(recoilW(p, PID::D0BAR), 1. / tau[1]);
      if (isSemileptonicDecay(p, {PID::D0BAR, PID::ANTIMUON, PID::NU_MU}))
        _h->fill(recoilW(p, PID::D0BAR), 1. / tau[1]);
    }
    else if (p.pid() == PID::B0) {
      _c->fill();
      if (isSemileptonicDecay(p, {PID::DMINUS, PID::POSITRON, PID::NU_E}))
        _h->fill(recoilW(p, PID::DMINUS), 1. / tau[0]);
      if (isSemileptonicDecay(p, {PID::DMINUS, PID::ANTIMUON, PID::NU_MU}))
        _h->fill(recoilW(p, PID::DMINUS), 1. / tau[0]);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h, 0.5 / *_c);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h;
CounterPtr _c;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEO_1997_I443704);

} ```