Rivet analyses

title: BABAR_2017_I1498564

Electron spectrum inclusive semi-leptonic in B decays

Experiment: BABAR (PEP-II)

Inspire ID: 1498564

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev. D95 (2017) no.7, 072001

Beams: * *

Beam energies: ANY

Run details: - bottom mesons produced at the Upsilon(4S)

Measurement of the electron spectrum inclusive semi-leptonic in $B$ decays, including both the total and the charmless. N.B. The spectum is obtained in the rest frame of the decaying $\Upsilon(4S)$ which produces the decaying $B$ mesons

Source code:BABAR_2017_I1498564.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Electron spectrum in B decays class BABAR_2017_I1498564 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2017_I1498564);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::pid == 300553), "UFS");
  // Book histograms
  // specify custom binning
  book(_h_light, 1, 1, 1);
  book(_h_all, 1, 1, 2);
  book(_nB, "/TMP/nB");
}


void findDecayProducts(Particle parent,
                       Particles& em,
                       Particles& ep,
                       Particles& nue,
                       Particles& nueBar,
                       bool& charm) {
  for (const Particle& p : parent.children()) {
    if (PID::isCharmHadron(p.pid())) {
      charm = true;
    }
    else if (p.pid() == PID::EMINUS) {
      em.push_back(p);
    }
    else if (p.pid() == PID::EPLUS) {
      ep.push_back(p);
    }
    else if (p.pid() == PID::NU_E) {
      nue.push_back(p);
    }
    else if (p.pid() == PID::NU_EBAR) {
      nueBar.push_back(p);
    }
    else if (PID::isBottomHadron(p.pid())) {
      findDecayProducts(p, em, ep, nue, nueBar, charm);
    }
    else if (!PID::isHadron(p.pid())) {
      findDecayProducts(p, em, ep, nue, nueBar, charm);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // find and loop over Upslion(4S)
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    // boost to rest frame
    LorentzTransform cms_boost;
    if (p.p3().mod() > 1 * MeV)
      cms_boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    // loop over decay products
    for (const Particle& p2 : p.children()) {
      if (p2.abspid() == 511 || p2.abspid() == 521) {
        _nB->fill();
        bool charm = false;
        Particles em, ep, nue, nueBar;
        findDecayProducts(p2, em, ep, nue, nueBar, charm);
        if (em.size() == 1 && nueBar.size() == 1) {
          double pmod = cms_boost.transform(em[0].momentum()).p3().mod();
          _h_all->fill(pmod);
          if (!charm) _h_light->fill(pmod);
        }
        else if (ep.size() == 1 && nue.size() == 1) {
          double pmod = cms_boost.transform(ep[0].momentum()).p3().mod();
          _h_all->fill(pmod);
          if (!charm) _h_light->fill(pmod);
        }
      }
    }
  }
}


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

  // normalize to number of B decays
  scale(_h_all, 1. / *_nB);
  scale(_h_light, 1. / *_nB);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_light, _h_all;
CounterPtr _nB;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2017_I1498564);

} ```