Rivet analyses

Lepton momentum spectrum in B → X_uℓν decays

Experiment: BABAR (PEP-II)

Inspire ID: 1079912

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 86 (2012) 032004

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+, B0 mesons, originally Upsilon(4S) decay

Measurement of the branching ratio for BX̄ → X_uℓν̄_ℓ for different lower cuts on the lepton momentum.

Source code:`BABAR_2012_I1079912.cc`

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

namespace Rivet {


  /// @brief B -> X_u ell nu
  class BABAR_2012_I1079912 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2012_I1079912);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // projections
      declare(UnstableParticles(Cuts::abspid == 511 or Cuts::abspid == 521), "UFS");
      // histograms
      book(_h, 1, 1, 1);
      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 || p.pid() == PID::NU_MU) {
          nue.push_back(p);
        }
        else if (p.pid() == PID::NU_EBAR || p.pid() == PID::NU_MUBAR) {
          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) {
      if (_edges.empty()) _edges = _h->xEdges();
      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
      for (const Particle& p : ufs.particles()) {
        if (p.children().empty()) continue;
        if (p.children()[0].abspid() == p.abspid()) continue;
        _nB->fill();
        bool charm = false;
        Particles em, ep, nue, nueBar;
        findDecayProducts(p, em, ep, nue, nueBar, charm);
        if (charm) continue;
        FourMomentum pl, pnu;
        if (em.size() == 1 && nueBar.size() == 1) {
          pl = em[0].momentum();
        }
        else if (ep.size() == 1 && nue.size() == 1) {
          pl = ep[0].momentum();
        }
        else
          continue;
        LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
        pl = boost.transform(pl);
        double pp = pl.p3().mod();
        double Emin = 1.0;
        for (unsigned int ix = 0; ix < _edges.size(); ++ix) {
          if (pp > Emin) _h->fill(_edges[ix]);
          Emin += 0.1;
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // 1e3 due br normalization and 0.1 to remove bin width
      scale(_h, 1e3 / *_nB);
    }

    /// @}


    /// @name Histograms
    /// @{
    BinnedHistoPtr<string> _h;
    CounterPtr _nB;
    vector<string> _edges;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BABAR_2012_I1079912);

}

Rivet analyses

Lepton momentum spectrum in B → Xuℓν decays

Source code:BABAR_2012_I1079912.cc

Lepton momentum spectrum in B → X_uℓν decays

Source code:`BABAR_2012_I1079912.cc`