Rivet analyses

title: BELLE_2021_I1895149

Differential Branching Fractions of Inclusive $B\to X_u\ell^+\nu_\ell$ decays

Experiment: BELLE (KEKB)

Inspire ID: 1895149

Status: VALIDATED SINGLEWEIGHT

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 127 (2021) 26, 261801

Beams: * *

Beam energies: ANY

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

Measurement of the $E^B_\ell$, $q^2$, $M_X$, $M^2_X$, $P_+$ and $P_-$ distributions in $B\to X_u\ell^+\nu_\ell$ decays by BELLLE.

Source code:BELLE_2021_I1895149.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> X_u l nu class BELLE_2021_I1895149 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2021_I1895149);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(), "UFS");
  // histograms
  for (unsigned int ix = 0; ix < 6; ++ix) {
    book(_h_direct[ix], 1 + ix, 1, 1);
    book(_h_forward[ix], "TMP/h_" + toString(ix + 1), refData(7 + ix, 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) {
  // find and loop over Upslion(4S)
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles(Cuts::pid == 300553)) {
    for (const Particle& p2 : p.children()) {
      if (p2.abspid() != 511 && p2.abspid() != 521) continue;
      _nB->fill();
      bool charm = false;
      Particles em, ep, nue, nueBar;
      findDecayProducts(p2, em, ep, nue, nueBar, charm);
      if (charm) continue;
      FourMomentum pl, pnu;
      if (em.size() == 1 && nueBar.size() == 1) {
        pl = em[0].momentum();
        pnu = nueBar[0].momentum();
      }
      else if (ep.size() == 1 && nue.size() == 1) {
        pl = ep[0].momentum();
        pnu = nue[0].momentum();
      }
      else
        continue;
      LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p2.momentum().betaVec());
      pl = boost.transform(pl);
      pnu = boost.transform(pnu);
      FourMomentum pB = boost.transform(p2.momentum());
      FourMomentum q = pl + pnu;
      FourMomentum pX = pB - q;
      double p3 = pX.p();
      _h_forward[0]->fill(pl.E());
      _h_forward[1]->fill(q.mass2());
      _h_forward[2]->fill(pX.mass());
      _h_forward[3]->fill(pX.mass2());
      _h_forward[4]->fill(pX.E() - p3);
      _h_forward[5]->fill(pX.E() + p3);
      if (pl.E() > 1) {
        _h_direct[0]->fill(pl.E());
        _h_direct[1]->fill(q.mass2());
        _h_direct[2]->fill(pX.mass());
        _h_direct[3]->fill(pX.mass2());
        _h_direct[4]->fill(pX.E() - p3);
        _h_direct[5]->fill(pX.E() + p3);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 0; ix < 6; ++ix) {
    // unfolded dist, scale by 1/2 /no of B's (2 as using e and mu modes)
    scale(_h_direct[ix], 0.5 / *_nB);
    // forward folding scale to BELLE no of B's
    scale(_h_forward[ix], 2. * 771.58e6 / *_nB);
    // get the efficiency product and divide by it
    unsigned int iloc = ix < 2 ? 3 + ix : (ix < 4 ? ix - 1 : ix + 1);
    Estimate1D eff = refData<YODA::Estimate1D>(iloc + 24, 1, 1);
    Estimate2D matrix = refData<YODA::Estimate2D>(19 + ix, 1, 1);
    // scatter for the result
    Estimate1DPtr corrected;
    book(corrected, ix + 7, 1, 1);
    vector<double> val(_h_forward[ix]->numBins(), 0.), err(_h_forward[ix]->numBins(), 0.);
    // first divide by eff
    for (unsigned int iy = 0; iy < _h_forward[ix]->numBins(); ++iy) {
      val[iy] = _h_forward[ix]->bin(iy + 1).sumW() / eff.bin(iy + 1).val();
      double relE = eff.bin(iy + 1).totalErrAvg() / eff.bin(iy + 1).val();
      err[iy] = val[iy] * sqrt(sqr(relE) + sqr(_h_forward[ix]->bin(iy + 1).relErrW()));
    }
    vector<double> val2(_h_forward[ix]->numBins(), 0.), err2(_h_forward[ix]->numBins(), 0.);
    for (unsigned int iy = 0; iy < _h_forward[ix]->numBins(); ++iy) {
      for (unsigned int iz = 0; iz < _h_forward[ix]->numBins(); ++iz) {
        double corr = matrix.bin((_h_forward[ix]->numBins() + 2) * (iz + 1) + iy + 1).val() / 100.;
        double ecorr = matrix.bin((_h_forward[ix]->numBins() + 2) * (iz + 1) + iy + 1).totalErrAvg()
            / 100.;
        val2[iy] += corr * val[iz];
        err2[iy] += sqr(ecorr * val[iz]) + sqr(corr * err[iz]);
      }
      err2[iy] = val2[iy] * sqrt(err2[iy] / sqr(val2[iy]) + sqr(9.78 / 771.58));
    }
    for (unsigned int ibin = 0; ibin < _h_forward[ix]->numBins(); ++ibin) {
      const double dy = sqrt(err[ibin]);
      corrected->bin(ibin + 1).set(val[ibin], dy);
    }
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_direct[6];
Histo1DPtr _h_forward[6];
CounterPtr _nB;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2021_I1895149);

} ```