Rivet analyses

title: BABAR_2009_I827787

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

Experiment: BABAR (PEP-II)

Inspire ID: 827787

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 81 (2010) 032003

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:BABAR_2009_I827787.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> Xc ell - nu_ell class BABAR_2009_I827787 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2009_I827787);


/// @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 < 6; ++ix) {
    book(_p_X[ix], 1, 1, 1 + ix);
    if (ix < 3) book(_p_n[ix], 2, 1, 1 + ix);
  }
}
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 || 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_X[0]->xEdges();
  static const double Lambda = 0.65 * GeV;
  // find and loop over Upslion(4S)
  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].momentum();
      pnu = nueBar[0].momentum();
    }
    else if (ep.size() == 1 && nue.size() == 1 && nue[0].pid() == -ep[0].pid() + 1) {
      pl = ep[0].momentum();
      pnu = nue[0].momentum();
    }
    else
      continue;
    // boost to rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    FourMomentum pX = boost.transform(p.momentum() - pl - pnu);
    pl = boost.transform(pl);
    double modp = pl.p3().mod();
    double mX = pX.mass();
    double nX2 = sqr(mX) - 2. * Lambda * pX.t() + sqr(Lambda);
    double m1 = mX, m2 = nX2;
    for (unsigned int ix = 0; ix < 6; ++ix) {
      double Emin = 0.8;
      for (unsigned int iy = 0; iy < _edges.size(); ++iy) {
        if (modp > Emin) _p_X[ix]->fill(_edges[iy], m1);
        Emin += 0.1;
      }
      m1 *= mX;
      if (ix >= 3) continue;
      Emin = 0.8;
      for (unsigned int iy = 0; iy < _edges.size(); ++iy) {
        if (modp > Emin) _p_n[ix]->fill(_edges[iy], m2);
        Emin += 0.1;
      }
      m2 *= nX2;
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
BinnedProfilePtr<string> _p_X[6], _p_n[3];
vector<string> _edges;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2009_I827787);

} ```