Rivet analyses

title: BABAR_2007_I722622

Spectrum for $\Xi_c^{\prime0,+}$ production at the $\Upsilon(4S)$

Experiment: BABAR (PEP-II)

Inspire ID: 722622

Status: VALIDATED

Authors: - Peter Richardson

References: - hep-ex/0607086

Beams: e+ e-

Beam energies: (5.3, 5.3)GeV

Run details: - e+e- > hadrons at Upsilon(4S) including both resonant and non-resonance

Spectrum for $\Xi_c^{\prime0,+}$ production at the $\Upsilon(4S)$ measured by BaBar. The spectrum includes a contribution from both the $\Upsilon(4S)$ and continuum $c\bar{c}$ events.

Source code:BABAR_2007_I722622.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Xi_c' spectrum class BABAR_2007_I722622 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I722622);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(), "UFS");
  // Book histograms
  book(_h_p_0, 3, 1, 2);
  book(_h_p_p, 3, 1, 1);
  book(_h_ctheta, 4, 1, 1);
  book(_b_p, 1, 1, 1);
  book(_b_0, 1, 1, 2);
  book(_r_p, 2, 1, 1);
  book(_r_0, 2, 1, 2);
  book(_ups, "/TMP/ups");
}

void findChildren(Particle parent, unsigned int& nStable, Particles& Xi, unsigned int& nPi) {
  for (const Particle& p : parent.children()) {
    if (p.abspid() == PID::PIPLUS) {
      ++nPi;
      ++nStable;
    }
    else if (p.abspid() == PID::XIMINUS) {
      Xi.push_back(p);
      ++nStable;
    }
    else if (!p.children().empty()) {
      findChildren(p, nStable, Xi, nPi);
    }
    else {
      ++nStable;
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  static const int id0 = 4312, idp = 4322;
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  bool ups = !ufs.particles(Cuts::pid == 300553).empty();
  if (ups) _ups->fill();
  for (const Particle& p : ufs.particles(Cuts::abspid == idp or Cuts::abspid == id0)) {
    int idXic = 4232;
    if (p.abspid() == idp) {
      _h_p_p->fill(p.momentum().p3().mod());
    }
    else {
      _h_p_0->fill(p.momentum().p3().mod());
      idXic = 4132;
    }
    // first find the Xi_c in the decay
    if (p.children().size() != 2) continue;
    int sign = p.pid() / p.abspid();
    Particle Xi_c;
    if (p.children()[0].pid() == sign * idXic && p.children()[1].pid() == 22) {
      Xi_c = p.children()[0];
    }
    else if (p.children()[1].pid() == sign * idXic && p.children()[0].pid() == 22) {
      Xi_c = p.children()[1];
    }
    else
      continue;
    // and the children of the Xi_c
    Particles Xi;
    unsigned int nStable(0), nPi(0);
    findChildren(Xi_c, nStable, Xi, nPi);
    if (Xi.size() != 1) continue;
    if (!(p.abspid() == idp && nPi == 2 && nStable == 3)
        && !(p.abspid() == id0 && nPi == 1 && nStable == 2))
      continue;
    if (p.abspid() == idp) {
      if (ups)
        _b_p->fill();
      else
        _r_p->fill("10.58"s);
    }
    else {
      if (ups)
        _b_0->fill();
      else
        _r_0->fill("10.58"s);
      idXic = 4132;
    }
    // boost to Xi'_c rest frame
    LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
    FourMomentum pXic = boost1.transform(Xi_c.momentum());
    FourMomentum pXi = boost1.transform(Xi[0].momentum());
    // then to Xi_c rest frame
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pXic.betaVec());
    Vector3 axis = pXic.p3().unit();
    FourMomentum pp = boost2.transform(pXi);
    // calculate angle
    double cTheta = pp.p3().unit().dot(axis);
    _h_ctheta->fill(cTheta);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  normalize(_h_p_0);
  normalize(_h_p_p);
  normalize(_h_ctheta);
  if (_ups->effNumEntries() != 0) {
    scale(_b_p, 0.5 / *_ups);
    scale(_b_0, 0.5 / *_ups);
  }
  scale(_r_p, crossSection() / sumOfWeights() / femtobarn);
  scale(_r_0, crossSection() / sumOfWeights() / femtobarn);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_p_0, _h_p_p, _h_ctheta;
CounterPtr _b_p, _b_0;
BinnedHistoPtr<string> _r_p, _r_0;
CounterPtr _ups;
/// @}

};

RIVET_DECLARE_PLUGIN(BABAR_2007_I722622);

} ```