Rivet analyses

K0, K̄0 and Λ0, Λ̄0 spectra at 14, 22 and 34 GeV

Experiment: TASSO (Petra)

Inspire ID: 205119

Status: VALIDATED

Authors: - Peter Richardson

References: - Z.Phys. C27 (1985) 27, 1985

Beams: e+ e-

Beam energies: (7.0, 7.0); (11.0, 11.0); (17.0, 17.0)GeV

Run details: - e+ e- to hadrons.

Measurement of the K0, K̄0 and Λ0, Λ̄0 spectra in e+e− collisions for centre-of-mass energies of 14, 22 and 34 GeV by the TASSO experiment at Petra.

Source code:TASSO_1985_I205119.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief K0 and Lambda spectra at 14, 22 and 34 GeV.
  class TASSO_1985_I205119 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(TASSO_1985_I205119);


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

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

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

      // 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 + "kaon_x"], 1 + ih, 1, 1);
        book(_h[en + "lambda_x"], 4 + ih, 1, 1);
        book(_h[en + "kaon_p"], 7 + ih, 1, 1);
        book(_h[en + "lambda_p"], 10 + ih, 1, 1);
        ++ih;
      }
      raiseBeamErrorIf(_sqs.empty());
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      // 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());
      MSG_DEBUG("Avg beam momentum = " << meanBeamMom);

      for (const Particle& p :
           apply<UnstableParticles>(event, "UFS")
               .particles(Cuts::abspid == PID::LAMBDA || Cuts::pid == 130 || Cuts::pid == 310)) {
        const double xE = p.E() / meanBeamMom;
        const double modp = p.p3().mod();
        const double beta = modp / p.E();
        if (p.abspid() == PID::LAMBDA) {
          _h[_sqs + "lambda_x"]->fill(xE, 1. / beta);
          _h[_sqs + "lambda_p"]->fill(modp, 1.);
        }
        else {
          _h[_sqs + "kaon_x"]->fill(xE, 1. / beta);
          _h[_sqs + "kaon_p"]->fill(modp, 1.);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (double eVal : allowedEnergies()) {
        const string en = toString(round(eVal / MeV));
        scale({_h[en + "kaon_x"], _h[en + "lambda_x"]},
              sqr(eVal) * crossSection() / microbarn / sumOfWeights());
        scale({_h[en + "kaon_p"], _h[en + "lambda_p"]}, crossSection() / nanobarn / sumOfWeights());
      }
    }

    /// @}


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


  RIVET_DECLARE_PLUGIN(TASSO_1985_I205119);
}