Rivet analyses

title: ARGUS_1986_I227324

Event shapes in $\Upsilon(1S)$ decay and nearby continuum

Experiment: ARGUS (DORIS)

Inspire ID: 227324

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C31 (1986) 181

Beams: e+ e-

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

Run details: - e+e- to hadrons for continuum and any process for Upsilon decay

Measurement of the thrust and sphericty by the ARGUS experiment in e+e- collision at the $\Upsilon(1S)$ resonance and in the nearby continuum.

Source code:ARGUS_1986_I227324.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/Sphericity.hh"

include "Rivet/Projections/Thrust.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Event shapes at Upsilon(1S) class ARGUS_1986_I227324 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1986_I227324);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(UnstableParticles(), "UFS");
  declare(ChargedFinalState(), "CFS");
  const FinalState fs;
  declare(Thrust(fs), "Thrust");
  declare(Sphericity(fs), "Sphericity");
  // histograms
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal, 1e-3)) _sqs = en;
    bool isCont(en == "9980"s);
    book(_h[en + "S"], 1, 1, 1 + isCont);
    book(_h[en + "T"], 2, 1, 1 + isCont);
  }
  raiseBeamErrorIf(_sqs.empty());
}

/// Recursively walk the decay tree to find the stable decay products of @a p
void findDecayProducts(const Particle& mother, Particles& charged, Particles& neutral) const {
  for (const Particle& p : mother.children()) {
    if (!p.children().empty()) {
      findDecayProducts(p, charged, neutral);
    }
    else {
      if (isCharged(p))
        charged.push_back(p);
      else
        neutral.push_back(p);
    }
  }
}


/// 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 or Cuts::pid == 100553);
  if (upsilons.empty() && _sqs == "9980"s) {
    Particles charged = apply<ChargedFinalState>(event, "CFS").particles();
    // at least 6 charged particles
    if (charged.size() < 6) vetoEvent;
    // cut on high momentum particles
    size_t nHigh(0);
    for (const Particle& p : charged) {
      if (p.mom().p3().mod() > 2.5) ++nHigh;
    }
    if (nHigh > 1) vetoEvent;
    MSG_DEBUG("No Upsilons found => continuum event");
    Thrust thrust = apply<Thrust>(event, "Thrust");
    _h[_sqs + "T"]->fill(thrust.thrust());
    Sphericity sphericity = apply<Sphericity>(event, "Sphericity");
    _h[_sqs + "S"]->fill(sphericity.sphericity());
  }
  else {
    for (const Particle& ups : upsilons) {
      LorentzTransform boost;
      if (ups.p3().mod() > 1 * MeV) {
        boost = LorentzTransform::mkFrameTransformFromBeta(ups.mom().betaVec());
      }
      // Find the decay products we want
      Particles charged, neutral;
      // 6 charged particles
      findDecayProducts(ups, charged, neutral);
      if (charged.size() < 6) continue;
      // at most 1 |p|>2.5
      vector<FourMomentum> mom;
      mom.reserve(neutral.size() + charged.size());
      unsigned int nHigh(0);
      for (const Particle& p : charged) {
        mom.push_back(boost.transform(p.mom()));
        if (mom.back().p3().mod() > 2.5) ++nHigh;
      }
      if (nHigh > 1) continue;
      for (const Particle& p : neutral) {
        mom.push_back(boost.transform(p.mom()));
      }
      Thrust thrust;
      thrust.calc(mom);
      _h[_sqs + "T"]->fill(thrust.thrust());
      Sphericity sphericity;
      sphericity.calc(mom);
      _h[_sqs + "S"]->fill(sphericity.sphericity());
    }
  }
}


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

/// @}


/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(ARGUS_1986_I227324);

} ```