Rivet analyses

title: ARGUS_1993_I342061

Production of the $\eta'(958)$ and $f_0(980)$ in $e^+e^-$ annihilation in the Upsilon region.

Experiment: ARGUS (DORIS)

Inspire ID: 342061

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C58 (1993) 199-206

Beams: e+ e-

Beam energies: (4.7, 4.7); (5.0, 5.0); (5.2, 5.2)GeV

Run details: - $e^+ e^-$ analysis near the $\Upsilon(4S)$ resonance.

Measurement of the inclusive production of the $\eta'(958)$ and $f_0(980)$ mesons in $e^+e^-$ annihilation in the Upsilon region. Data are taken on the $\Upsilon(1S)$, $\Upsilon(2S)$ and $\Upsilon(4S)$ resonances and in the nearby continuum (9.36 to 10.45 GeV center-of-mass energy)

Source code:ARGUS_1993_I342061.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Production of the $\eta'(958)$ and $f_0(980)$ in $e^+e^-$ annihilation in the Upsilon region /// /// @author Peter Richardson class ARGUS_1993_I342061 : public Analysis { public:

RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1993_I342061);


void init() {
  declare(UnstableParticles(), "UFS");

  book(_weightSum_cont, "TMP/weightSum_cont");
  book(_weightSum_Ups1, "TMP/weightSum_Ups1");
  book(_weightSum_Ups2, "TMP/weightSum_Ups2");

  book(_count_etaPrime_highZ, 1, 1, 1);
  book(_count_etaPrime_allZ, 1, 1, 2);
  book(_count_f0, 5, 1, 1);

  book(_hist_cont_f0, 2, 1, 1);
  book(_hist_Ups1_f0, 3, 1, 1);
  book(_hist_Ups2_f0, 4, 1, 1);
}


void analyze(const Event& e) {
  // Find the Upsilons among the unstables
  const UnstableParticles& ufs = apply<UnstableParticles>(e, "UFS");
  Particles upsilons = ufs.particles(Cuts::pid == 553 or Cuts::pid == 100553);
  // Continuum
  if (upsilons.empty()) {
    MSG_DEBUG("No Upsilons found => continuum event");
    _weightSum_cont->fill();
    for (const Particle& p : ufs.particles()) {
      const int id = p.pid();
      const double xp = 2. * p.E() / sqrtS();
      const double beta = p.p3().mod() / p.E();
      if (id == 9010221) {
        _hist_cont_f0->fill(xp, 1. / beta);
        _count_f0->fill(string("10.45"));
      }
      else if (id == 331) {
        if (xp > 0.35) _count_etaPrime_highZ->fill(string("9.36 - 10.45"));
        _count_etaPrime_allZ->fill(string("9.36 - 10.45"));
      }
    }
  }
  // Upsilon(s) found
  else {
    for (const Particle& ups : upsilons) {
      const int parentId = ups.pid();
      if (parentId == 553) {
        _weightSum_Ups1->fill();
      }
      else {
        _weightSum_Ups2->fill();
      }
      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.momentum().betaVec());
      const double mass = ups.mass();
      // loop over decay products
      for (const Particle& p : unstable) {
        const int id = p.pid();
        const FourMomentum p2 = cms_boost.transform(p.momentum());
        const double xp = 2. * p2.E() / mass;
        const double beta = p2.p3().mod() / p2.E();
        if (id == 9010221) {
          if (parentId == 553) {
            _hist_Ups1_f0->fill(xp, 1. / beta);
            _count_f0->fill(string("9.46"));
          }
          else {
            _hist_Ups2_f0->fill(xp, 1. / beta);
            _count_f0->fill(string("10.02"));
          }
        }
        else if (id == 331) {
          if (parentId == 553) {
            if (xp > 0.35) _count_etaPrime_highZ->fill(string("9.46"));
            _count_etaPrime_allZ->fill(string("9.46"));
          }
          else {
            _count_etaPrime_allZ->fill(string("10.02"));
          }
        }
      }
    }
  }
}

void finalize() {
  // Point at 9.905
  if (_weightSum_cont->val() > 0) {
    _count_etaPrime_highZ->binAt(string("9.36 - 10.45")).scaleW(1. / _weightSum_cont->val());
    _count_etaPrime_allZ->binAt(string("9.36 - 10.45")).scaleW(1. / _weightSum_cont->val());
    _count_f0->binAt(string("10.45")).scaleW(1. / _weightSum_cont->val());
  }
  // Point at 9.460
  if (_weightSum_Ups1->val() > 0) {
    _count_etaPrime_highZ->binAt(string("9.46")).scaleW(1. / _weightSum_Ups1->val());
    _count_etaPrime_allZ->binAt(string("9.46")).scaleW(1. / _weightSum_Ups1->val());
    _count_f0->binAt(string("9.46")).scaleW(1. / _weightSum_Ups1->val());
  }
  // Point at 10.02
  if (_weightSum_Ups2->val() > 0) {
    _count_etaPrime_allZ->binAt(string("10.02")).scaleW(1. / _weightSum_Ups2->val());
    _count_f0->binAt(string("10.02")).scaleW(1. / _weightSum_Ups2->val());
  }
  // Scale histos
  if (_weightSum_cont->val() > 0.) scale(_hist_cont_f0, 1. / *_weightSum_cont);
  if (_weightSum_Ups1->val() > 0.) scale(_hist_Ups1_f0, 1. / *_weightSum_Ups1);
  if (_weightSum_Ups2->val() > 0.) scale(_hist_Ups2_f0, 1. / *_weightSum_Ups2);
}

private:

/// @name Counters
/// @{
BinnedHistoPtr<string> _count_etaPrime_highZ, _count_etaPrime_allZ, _count_f0;
CounterPtr _weightSum_cont, _weightSum_Ups1, _weightSum_Ups2;
/// @}


/// Histos
Histo1DPtr _hist_cont_f0, _hist_Ups1_f0, _hist_Ups2_f0;


/// 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 == 331 || id == 9010221) {
      unstable.push_back(p);
    }
    else if (!p.children().empty()) {
      findDecayProducts(p, unstable);
    }
  }
}

};

RIVET_DECLARE_ALIASED_PLUGIN(ARGUS_1993_I342061, ARGUS_1993_S2669951);

} ```

Aliases: - ARGUS_1993_S2669951