Rivet analyses

title: ARGUS_1989_I262415

Spectra for the production of $\Lambda^0(1520)$ in $e^+e^-$ collisions in the continuum at 10 GeV and the $\Upsilon_1$

Experiment: ARGUS (DORIS)

Inspire ID: 262415

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett. B215 (1988) 429-434, 1988

Beams: e- e+

Beam energies: (4.7, 4.7); (5.0, 5.0)GeV

Run details: - $e^+ e^-$ analysis near the $\Upsilon$ resonances

Spectra for the production of $\Lambda^0(1520)$ in $e^+e^-$ collisions. Data are taken on the $\Upsilon(1S)$ and in the nearby continuum.

Source code:ARGUS_1989_I262415.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda(1520) production class ARGUS_1989_I262415 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1989_I262415);


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

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  declare(UnstableParticles(), "UFS");

  // Book histograms
  book(_h_ups1_obs, 1, 1, 1);
  book(_h_cont_obs, 1, 1, 2);
  book(_h_ups1_all, 1, 2, 1);
  book(_h_cont_all, 1, 2, 2);
  book(_h_ups1, 3, 1, 1);
  book(_h_cont, 4, 1, 1);
  book(_weightSum_cont, "TMP/weightSum_cont");
  book(_weightSum_Ups1, "TMP/weightSum_Ups1");
}

/// Recursively walk the decay tree to find decay products of @a p
void findDecayProducts(Particle mother, Particles& unstable) {
  for (const Particle& p : mother.children()) {
    const int id = p.pid();
    if (id == 102134) {
      unstable.push_back(p);
    }
    if (!p.children().empty()) findDecayProducts(p, unstable);
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // Find the Upsilons among the unstables
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  Particles upsilons = ufs.particles(Cuts::pid == 553);
  // Continuum
  if (upsilons.empty()) {
    MSG_DEBUG("No Upsilons found => continuum event");
    _weightSum_cont->fill();
    for (const Particle& p : ufs.particles(Cuts::abspid == 102134)) {
      const double xp = 2. * p.E() / sqrtS();
      const double beta = p.p3().mod() / p.E();
      _h_cont->fill(xp, 1. / beta);
      _h_cont_obs->fill(xp);
      _h_cont_all->fill(xp);
    }
  }
  // Upsilon(s) found
  else {
    MSG_DEBUG("Upsilons found => resonance event");
    for (const Particle& ups : upsilons) {
      _weightSum_Ups1->fill();
      Particles unstable;
      // Find the decay products we want
      findDecayProducts(ups, unstable);
      LorentzTransform cms_boost;
      if (ups.p3().mod() > 1 * MeV)
        cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
      const double mass = ups.mass();
      // loop over decay products
      for (const Particle& p : unstable) {
        const FourMomentum p2 = cms_boost.transform(p.momentum());
        const double xp = 2. * p2.E() / mass;
        const double beta = p2.p3().mod() / p2.E();
        _h_ups1->fill(xp, 1. / beta);
        _h_ups1_obs->fill(xp);
        _h_ups1_all->fill(xp);
      }
    }
  }
}

/// Normalise histograms etc., after the run
void finalize() {
  if (_weightSum_cont->val() > 0.) {
    scale(_h_cont, 1. / *_weightSum_cont);
    scale(_h_cont_obs, 0.3 / *_weightSum_cont);
    scale(_h_cont_all, 1. / *_weightSum_cont);
  }
  if (_weightSum_Ups1->val() > 0.) {
    scale(_h_ups1, 1. / *_weightSum_Ups1);
    scale(_h_ups1_obs, 0.3 / *_weightSum_Ups1);
    scale(_h_ups1_all, 1. / *_weightSum_Ups1);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_ups1, _h_cont;
Histo1DPtr _h_ups1_obs, _h_cont_obs;
Histo1DPtr _h_ups1_all, _h_cont_all;
CounterPtr _weightSum_cont, _weightSum_Ups1;
/// @}

};

RIVET_DECLARE_PLUGIN(ARGUS_1989_I262415);

} ```