Rivet analyses

title: ARGUS_1992_I319829

$D^+_s$ production in $e^+e^-$ annihilation at 10.5 GeV, and $B$ decays

Experiment: ARGUS (DORIS)

Inspire ID: 319829

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Z.Phys.C 54 (1992) 1-12

Beams: e- e+

Beam energies: ANY

Run details: - e+e- to hadrons, at 10.47 GeV, or Upsilon(4S) (10.58)

Measurement of the scaled momentum spectra for $D^+_s$ production in $e^+e^-$ annihilation at 10.5 GeV, and from $B$ decays at the $\Upsilon(4S)$.

Source code:ARGUS_1992_I319829.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief D_s+ in B or continuum class ARGUS_1992_I319829 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1992_I319829);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(UnstableParticles(), "UFS");
  declare(Beam(), "Beams");
  // histos
  book(_n_Ds, 1, 1, 1);
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h_Ds[ix], 2 + ix, 1, 1);
  }
}

/// Recursively walk the decay tree to find decay products of @a p
void findDecayProducts(const Particle& mother, Particles& unstable) {
  for (const Particle& p : mother.children()) {
    const int id = p.abspid();
    if (id == 431) {
      unstable.push_back(p);
    }
    else if (!p.children().empty()) {
      findDecayProducts(p, unstable);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // Get beams and average beam momentum
  const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
  const double meanBeamMom = 0.5 * (beams.first.p3().mod() + beams.second.p3().mod());
  MSG_DEBUG("Avg beam momentum = " << meanBeamMom);
  // Find the Upsilon(4S) among the unstables
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  Particles upsilons = ufs.particles(Cuts::pid == 300553);
  // Continuum
  if (upsilons.empty()) {
    for (const Particle& p : ufs.particles(Cuts::abspid == 431)) {
      const double xp = p.p3().mod() / sqrt(sqr(meanBeamMom) - sqr(p.mass()));
      _h_Ds[0]->fill(xp);
      _n_Ds->fill(10);
    }
  }
  else {
    for (const Particle& ups : upsilons) {
      Particles unstable;
      // Find the decay products we want
      findDecayProducts(ups, unstable);
      // boost to rest frame (if required)
      LorentzTransform cms_boost;
      if (ups.p3().mod() > 1 * MeV) {
        cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.mom().betaVec());
      }
      for (const Particle& p : unstable) {
        const FourMomentum p2 = cms_boost.transform(p.mom());
        double xp = p2.p3().mod() / sqrt(0.25 * sqr(ups.mass()) - sqr(p.mass()));
        _h_Ds[1]->fill(xp);
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // bre d+s -> phi pi+
  const double br = 0.045;
  normalize(_h_Ds, 1.0, false);
  scale(_n_Ds, br / sumOfWeights() * crossSection() / picobarn);
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<int> _n_Ds;
Histo1DPtr _h_Ds[2];
/// @}

};

RIVET_DECLARE_PLUGIN(ARGUS_1992_I319829);

} ```