Rivet analyses

title: BELLE_2007_I732595

Hadronic mass moments in $B\to X_c\ell^-\bar\nu_\ell$

Experiment: BELLE (KEKB)

Inspire ID: 732595

Status: VALIDATED NOHEPDATA SINGLEWEIGHT

Authors: - Peter Richardson

References: - Phys.Rev.D 75 (2007) 032005

Beams: * *

Beam energies: ANY

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

Measurement of the moments of the hadronic mass in $B\to X_c\ell^-\bar\nu_\ell$.

Source code:BELLE_2007_I732595.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> Xc ell - nu_ell class BELLE_2007_I732595 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I732595);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(Cuts::abspid == 511 || Cuts::abspid == 521), "UFS");
  // histograms
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_p[ix], 1, 1, 1 + 2 * ix);
  }
}

void findDecayProducts(const 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 || p.pid() == PID::MUON) {
      em.push_back(p);
    }
    else if (p.pid() == PID::EPLUS || p.pid() == PID::ANTIMUON) {
      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 = _p[0]->xEdges();
    for (const string& en : _edges) _eCut.push_back(std::stod(en) * GeV);
  }
  // find and loop over B mesons
  for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
    if (p.children().empty() || (p.children().size() == 1 && p.children()[1].abspid() == p.abspid()))
      continue;
    // find decay products
    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 && em[0].pid() + 1 == -nueBar[0].pid()) {
      pl = em[0].mom();
      pnu = nueBar[0].mom();
    }
    else if (ep.size() == 1 && nue.size() == 1 && nue[0].pid() == -ep[0].pid() + 1) {
      pl = ep[0].mom();
      pnu = nue[0].mom();
    }
    else {
      continue;
    }
    // boost to rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.mom().betaVec());
    double mX2 = (p.mom() - pl - pnu).mass2();
    pl = boost.transform(pl);
    double Estar = pl.E();
    for (unsigned int ix = 0; ix < 2; ++ix) {
      for (unsigned int ix = 0; ix < _eCut.size(); ++ix) {
        if (Estar > _eCut[ix]) {
          _p[0]->fill(_edges[ix], mX2);
          _p[1]->fill(_edges[ix], sqr(mX2));
        }
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // compute <(mx2-<mx2>)^2> = <mx4>-<mx2>^2
  BinnedEstimatePtr<string> tmp;
  book(tmp, 1, 1, 2);
  for (unsigned int ix = 0; ix < _p[0]->numBins(); ++ix) {
    const double value = _p[1]->bin(ix + 1).mean(2) - sqr(_p[0]->bin(ix + 1).mean(2));
    const double error = value
        * sqrt(sqr(_p[1]->bin(ix + 1).relStdErr(2)) + 4. * sqr(_p[0]->bin(ix + 1).relStdErr(2)));
    tmp->bin(ix + 1).set(value, error);
  }
}

/// @}


/// @name Histograms
/// @{
BinnedProfilePtr<string> _p[2];
vector<string> _edges;
vector<double> _eCut;
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2007_I732595);

} ```