Rivet analyses

title: LENA_1981_I164397

Charged particle multiplicities and thrust in $\Upsilon(1S,2S)$ decays and nearby continuum

Experiment: LENA (DORIS)

Inspire ID: 164397

Status: VALIDATED

Authors: - Peter Richardson

References: none listed

Beams: * *

Beam energies: ANY

Run details: - e+e- to hadrons for continuum, or any process producing Upsilon 1S and 2S decays

Measurement of the charged particle multiplicities and a thrust-like variable in $\Upsilon(1S,2S)$ decays and nearby continuum. As LENA had no magnetic field the momenta of the charged particles were not measured and therefore a thrust-like variable $T^\prime$ was constructed using only the directions of the charged particles.

Source code:LENA_1981_I164397.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/Thrust.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Thrust like variable at Upsilon(1S,2S) class LENA_1981_I164397 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LENA_1981_I164397);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(), "UFS");
  declare(ChargedFinalState(), "FS");
  const double eval = sqrtS() / GeV;
  if (inRange(eval, 7.35, 7.49)) {
    _sqs = "7.35 - 7.49"s;
  }
  else if (inRange(eval, 8.629, 9.142)) {
    _sqs = "8.629 - 9.142"s;
  }
  else if (inRange(eval, 9.15, 9.41)) {
    _sqs = "9.15 - 9.41"s;
  }
  else if (isCompatibleWithSqrtS(9.5149, 1e-2)) {
    _sqs = "9.5149";
  }
  else if (isCompatibleWithSqrtS(9.9903, 1e-2)) {
    _sqs = "9.9903";
  }
  else if (isCompatibleWithSqrtS(9.4624, 1e-2)) {
    _sqs = "9.4624";
  }
  else if (isCompatibleWithSqrtS(10.0148, 1e-2)) {
    _sqs = "10.0148";
  }
  else
    raiseBeamErrorIf(true);
  book(_mult, 3, 1, 1);
  book(_h["9.5149"], 4, 1, 1);
  book(_h["9.9903"], 4, 1, 2);
  book(_h["9.4624"], 4, 1, 3);
  book(_h["10.0148"], 4, 1, 4);
  book(_c["9.5149"], "TMP/weightSum_cont1");
  book(_c["9.9903"], "TMP/weightSum_cont2");
  book(_c["9.4624"], "TMP/weightSum_Ups1");
  book(_c["10.0148"], "TMP/weightSum_Ups2");
}


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

// defn of thrust in paper used just the direction
double thrustPrime(const LorentzTransform& boost, const Particles& particles) const {
  vector<Vector3> vecs;
  vecs.reserve(particles.size());
  for (const Particle& p : particles) {
    vecs.push_back(boost.transform(p.mom()).p3());
  }
  Thrust thrust;
  thrust.calc(vecs);
  return thrust.thrust();
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  // Find the Upsilons among the unstables
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  const Particles upsilons = ufs.particles(Cuts::pid == 553 or Cuts::pid == 100553);
  if (upsilons.empty()) {
    MSG_DEBUG("No Upsilons found => continuum event");
    const Particles cfs = apply<ChargedFinalState>(event, "FS").particles();
    _mult->fill(_sqs, cfs.size());
    if (_sqs == "9.5149"s or _sqs == "9.9903"s) {
      _c[_sqs]->fill();
      LorentzTransform boost;
      _h[_sqs]->fill(thrustPrime(boost, cfs));
    }
  }
  // Upsilon(s) found
  else {
    for (const Particle& ups : upsilons) {
      const int parentId = ups.pid();
      Particles charged;
      // boost to rest frame (if required)
      LorentzTransform boost;
      if (ups.p3().mod() > 1 * MeV)
        boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
      // Find the decay products we want
      findDecayProducts(ups, charged);
      if (parentId == 553) {
        _c["9.4624"s]->fill();
        _mult->fill("9.4624"s, charged.size());
        _h["9.4624"s]->fill(thrustPrime(boost, charged));
      }
      else if (parentId == 100553) {
        _c["10.0148"s]->fill();
        _mult->fill("10.0148"s, charged.size());
        _h["10.0148"s]->fill(thrustPrime(boost, charged));
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // charged particle multiplicity
  scale(_h, crossSectionPerEvent());
  scale(_c, crossSectionPerEvent());
  for (const auto& item : _c) {
    const double w = item.second->val();
    if (isZero(w)) continue;
    scale(_h[item.first], 1.0 / w);
  }
}

/// @}


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

};

RIVET_DECLARE_PLUGIN(LENA_1981_I164397);

} ```