Rivet analyses

title: TASSO_1989_I266893

Spectra for $\Lambda^0,\bar{\Lambda}^0$ and $\Xi^-,\bar{\Xi}^-$ at 34.8 and 42.1 GeV

Experiment: TASSO (Petra)

Inspire ID: 266893

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C45 (1989) 209, 1989

Beams: e+ e-

Beam energies: (17.4, 17.4); (21.1, 21.1)GeV

Run details: - e+ e- to hadrons.

Measurement of the $\Lambda^0,\bar{\Lambda}^0$ and $\Xi^-,\bar{\Xi}^-$ spectra at 34.8 and 42.1 GeV by the TASSO experiment at Petra. In addition to the spectra $p_l$, $p_\perp^{\text{in}}$, $p_\perp^{\text{out}}$ and the rapidity of the $\Lambda^0,\bar{\Lambda}^0$ are measured with respect to the sphericity axis.

Source code:TASSO_1989_I266893.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/Beam.hh"

include "Rivet/Projections/ChargedFinalState.hh"

include "Rivet/Projections/Sphericity.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief baryons at 34.8 and 42.1 GeV class TASSO_1989_I266893 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1989_I266893);

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

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

  // Initialise and register projections
  declare(Beam(), "Beams");
  declare(UnstableParticles(), "UFS");
  const ChargedFinalState cfs;
  declare(cfs, "CFS");
  declare(Sphericity(cfs), "Sphericity");

  // Book histograms
  size_t ih = 0;
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal)) _sqs = en;
    book(_h[en + "lam_p"], 6 * ih + 3, 1, 1);
    book(_h[en + "lam_pL"], 6 * ih + 4, 1, 1);
    book(_h[en + "lam_pTIn"], 6 * ih + 5, 1, 1);
    book(_h[en + "lam_pTOut"], 6 * ih + 6, 1, 1);
    book(_h[en + "lam_rap"], 6 * ih + 7, 1, 1);
    book(_h[en + "lam_x"], 6 * ih + 8, 1, 1);
    book(_p[en + "lam_S_1"], 15 + ih, 1, 1);
    book(_p[en + "lam_S_2"], 15 + ih, 1, 2);
    if (en == "34800"s) {
      book(_h["xi_p"], 18, 1, 1);
      book(_h["xi_pL"], 19, 1, 1);
      book(_h["xi_pTIn"], 20, 1, 1);
      book(_h["xi_pTOut"], 21, 1, 1);
      book(_h["xi_rap"], 22, 1, 1);
      book(_h["xi_x"], 23, 1, 1);
    }
    ++ih;
  }
  raiseBeamErrorIf(_sqs.empty());
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");
  const size_t numParticles = cfs.particles().size();

  // Even if we only generate hadronic events, we still need a cut on numCharged >= 2.
  if (numParticles < 2) vetoEvent;

  // 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());
  const Sphericity& sphericity = apply<Sphericity>(event, "Sphericity");
  unsigned int nLam(0);
  UnstableParticles ufs = apply<UnstableParticles>(event, "UFS");
  for (const Particle& p : ufs.particles(Cuts::abspid == 3122 || Cuts::abspid == 3312)) {
    unsigned int id = p.abspid();
    double xE = p.E() / meanBeamMom;
    Vector3 mom3 = p.p3();
    const double energy = p.E();
    double modp = mom3.mod();
    double beta = modp / energy;
    const double momS = dot(sphericity.sphericityAxis(), mom3);
    const double pTinS = dot(mom3, sphericity.sphericityMajorAxis());
    const double pToutS = dot(mom3, sphericity.sphericityMinorAxis());
    const double rapidityS = 0.5 * std::log((energy + momS) / (energy - momS));
    if (id == 3122) {
      _h[_sqs + "lam_x"]->fill(xE, 1. / beta);
      _h[_sqs + "lam_p"]->fill(modp / GeV);
      _h[_sqs + "lam_pL"]->fill(abs(momS) / GeV);
      _h[_sqs + "lam_pTIn"]->fill(abs(pTinS) / GeV);
      _h[_sqs + "lam_pTOut"]->fill(abs(pToutS) / GeV);
      _h[_sqs + "lam_rap"]->fill(abs(rapidityS));
      ++nLam;
    }
    else if (_sqs == "34800"s) {
      _h["xi_x"]->fill(xE, 1. / beta);
      _h["xi_p"]->fill(modp / GeV);
      _h["xi_pL"]->fill(abs(momS) / GeV);
      _h["xi_pTIn"]->fill(abs(pTinS) / GeV);
      _h["xi_pTOut"]->fill(abs(pToutS) / GeV);
      _h["xi_rap"]->fill(abs(rapidityS));
    }
  }
  const double sphere = sphericity.sphericity();
  _p[_sqs + "lam_S_1"]->fill(sphere, nLam);
  _p[_sqs + "lam_S_2"]->fill(sphere, cfs.particles().size());
}


/// Normalise histograms etc., after the run
void finalize() {
  size_t ih = 0;
  Estimate1DPtr temp;
  scale(_h, crossSection() / nanobarn / sumOfWeights());
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal / MeV));
    scale(_h[en + "lam_x"], sqr(eVal));
    if (en == "34800"s) scale(_h["xi_x"], sqr(eVal));
    book(temp, 15 + ih, 1, 3);
    divide(_p[en + "lam_S_1"], _p[en + "lam_S_2"], temp);
    ++ih;
  }
}

/// @}


/// @name Histograms
/// @{
map<string, Histo1DPtr> _h;
map<string, Profile1DPtr> _p;
string _sqs = "";
/// @}

};

RIVET_DECLARE_PLUGIN(TASSO_1989_I266893); } ```