Rivet analyses

title: CLEOII_1997_I440969

Momenta spectra and polarization in $B\to D^{(*)}$ decays

Experiment: CLEOII (CESR)

Inspire ID: 440969

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 56 (1997) 3783-3802

Beams: * *

Beam energies: ANY

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

Measurement of the momenta spectrra for the production of $D^0$, D$^+$, $D^{0}$ and $D^{+}$ mesons in $B$ decays by CLEO. The polarization of the $D^*$ mesons in also measured.

Source code:CLEOII_1997_I440969.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

include "Rivet/Tools/HistoGroup.hh"

namespace Rivet {

/// @brief D spect in B decays class CLEOII_1997_I440969 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1997_I440969);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::pid == 300553), "UFS");
  // histos
  const vector<double> xbins = {0.0, 0.1, 0.2, 0.3, 0.4, 0.5};
  for (unsigned int ix = 0; ix < 4; ++ix) {
    book(_h[ix], 1 + ix, 1, 1);
  }
  book(_b[0], {0.1, 0.2, 0.3, 0.4, 0.5});
  book(_b[1], {0.0, 0.1, 0.2, 0.3, 0.4, 0.5});
  for (auto& b : _b[1]->bins()) {
    book(b, 6, 1, b.index());
    if (b.index() < 5) {
      book(_b[0]->bin(b.index()), 5, 1, b.index());
    }
  }
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_p[ix], "TMP/p_" + toString(ix + 1), refData(7, 1, 1 + ix));
  }
}

void findDecay(const Particle& parent, Particles& Ds) {
  for (const Particle& p : parent.children()) {
    if (p.abspid() == 421 || p.abspid() == 411) {
      Ds.push_back(p);
    }
    else if (p.abspid() == 413 || p.abspid() == 423) {
      Ds.push_back(p);
      findDecay(p, Ds);
    }
    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, Ds);
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles()) {
    const LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.mom().betaVec());
    for (const Particle& B : p.children()) {
      if (B.abspid() != 511 && B.abspid() != 521) continue;
      Particles Ds;
      findDecay(B, Ds);
      for (const Particle& p2 : Ds) {
        FourMomentum pD = boost.transform(p2.mom());
        const double x = pD.p3().mod() / sqrt(0.25 * sqr(p.mass()) - sqr(p2.mass()));
        if (p2.abspid() == 421)
          _h[0]->fill(x);
        else if (p2.abspid() == 411)
          _h[1]->fill(x);
        else {
          // x distribution for D*
          if (p2.abspid() == 423)
            _h[2]->fill(x);
          else
            _h[3]->fill(x);
          // find decay products
          if (p2.children().size() != 2) continue;
          Particle dec;
          if ((p2.children()[0].abspid() == 411 || p2.children()[0].abspid() == 421)
              && (p2.children()[1].abspid() == 111 || p2.children()[1].abspid() == 211)) {
            dec = p2.children()[0];
          }
          else if ((p2.children()[1].abspid() == 411 || p2.children()[1].abspid() == 421)
                   && (p2.children()[0].abspid() == 111 || p2.children()[0].abspid() == 211)) {
            dec = p2.children()[1];
          }
          else
            continue;
          const LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pD.betaVec());
          FourMomentum pDec = boost2.transform(boost.transform(dec.momentum()));
          // decay angle
          double cTheta = pDec.p3().unit().dot(pD.p3().unit());
          if (p2.abspid() == 423) {
            _b[1]->fill(x, cTheta);
            _p[1]->fill(x, -1. / 2. * (1. - 5. * sqr(cTheta)));
          }
          else {
            _b[0]->fill(x, cTheta);
            _p[0]->fill(x, -1. / 2. * (1. - 5. * sqr(cTheta)));
          }
        }
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // spectra
  normalize(_h, 1.0, false);
  for (unsigned int ix = 0; ix < 2; ++ix) {
    // angles dists
    normalize(_b[ix], 1.0, false);
    // polarizations
    Estimate1DPtr tmp;
    book(tmp, 7, 1, 1 + ix);
    for (const auto& b : _p[ix]->bins()) {
      const double val = b.numEntries() > 0 && b.effNumEntries() > 0 ? b.yMean() : 0.;
      const double err = b.numEntries() > 1 && b.effNumEntries() > 1 ? b.yStdErr() : 0.;
      const double l1 = 2. * val / (1. + val);
      const double e1 = 2. / sqr(1. + val) * err;
      tmp->bin(b.index()).set(l1, e1);
    }
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h[4];
Profile1DPtr _p[2];
Histo1DGroupPtr _b[2];
/// @}

};

RIVET_DECLARE_PLUGIN(CLEOII_1997_I440969);

} ```