Rivet analyses

title: CLEOII_1996_I398228

$\eta$ momentum spectrum in $B$ decays

Experiment: CLEOII (CESR)

Inspire ID: 398228

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 53 (1996) 6033-6036

Beams: * *

Beam energies: ANY

Run details: - Any process producing Upsilon(4S), originally e+e-

Measurement of the $\eta$ momentum spectrum in $B$ decays. The data were taken from table I in the paper.

Source code:CLEOII_1996_I398228.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> eta X class CLEOII_1996_I398228 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1996_I398228);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::pid == 300553), "UFS");
  // histograms
  book(_w_ups4, "/TMP/w_ups4");
  book(_h, 1, 1, 1);
}

void findDecay(const Particle& parent, Particles& eta) {
  for (const Particle& p : parent.children()) {
    if (p.pid() == PID::ETA) {
      eta.push_back(p);
    }
    else if (p.abspid() == PID::PIPLUS || p.abspid() == PID::KPLUS || p.pid() == PID::PI0
             || p.pid() == PID::K0S) {
      continue;
    }
    else if (!p.children().empty()) {
      findDecay(p, eta);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles()) {
    _w_ups4->fill();
    const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.mom().betaVec());
    for (const Particle& B : p.children()) {
      if (B.abspid() != 511 && B.abspid() != 521) continue;
      Particles eta;
      findDecay(B, eta);
      for (const Particle& p2 : eta) {
        double pEta = boost.transform(p2.mom()).p3().mod();
        _h->fill(pEta);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // 2 B's per upsilon and in percent
  scale(_h, 50. / *_w_ups4);
}

/// @}


/// @name Histograms
/// @{
CounterPtr _w_ups4;
Histo1DPtr _h;
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_1996_I398228);

} ```