Rivet analyses

UA5 multiplicity and pseudorapidity distributions for pp and pp̄.

Experiment: UA5 (SPS)

Inspire ID: 176647

Status: VALIDATED

Authors: - Andy Buckley - Christophe Vaillant

References: - Phys.Lett.112B:183,1982

Beams: p- p+, p+ p+

Beam energies: (26.5, 26.5)GeV

Run details: - Min bias QCD events at $\sqrt{s} = 53$~GeV. Run with both pp and pp̄ beams.

Comparisons of multiplicity and pseudorapidity distributions for pp and pp̄ collisions at 53 GeV, based on the UA5 53~GeV runs in 1982. Data confirms the lack of significant difference between the two beams.

Source code:UA5_1982_I176647.cc

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/ChargedFinalState.hh"
#include "Rivet/Projections/TriggerUA5.hh"

namespace Rivet {


  /// UA5 multiplicity and \f$ \eta \f$ distributions
  class UA5_1982_I176647 : public Analysis {
  public:

    /// Default constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(UA5_1982_I176647);


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

    /// Set up projections and book histos
    void init() {
      declare(TriggerUA5(), "Trigger");
      declare(ChargedFinalState((Cuts::etaIn(-3.5, 3.5))), "CFS");

      // Book histos based on pp or ppbar beams
      if (beamIDs().first == beamIDs().second) {
        book(_hist_nch ,2,1,1);
        book(_hist_eta ,3,1,1);
      } else {
        book(_hist_nch ,2,1,2);
        book(_hist_eta ,4,1,1);
      }
      book(_sumWTrig, "sumW");

    }


    void analyze(const Event& event) {
      // Trigger
      const TriggerUA5& trigger = apply<TriggerUA5>(event, "Trigger");
      if (!trigger.nsdDecision()) vetoEvent;
      _sumWTrig->fill();

      // Get tracks
      const ChargedFinalState& cfs = apply<ChargedFinalState>(event, "CFS");

      // Fill mean charged multiplicity histos
      _hist_nch->fill(53, cfs.size());

      // Iterate over all tracks and fill eta histograms
      for (const Particle& p : cfs.particles()) {
        const double eta = p.abseta();
        _hist_eta->fill(eta);
      }

    }


    void finalize() {
      /// @todo Why the factor of 2 on Nch for ppbar?
      if (beamIDs().first == beamIDs().second) {
        scale(_hist_nch, 1.0 / *_sumWTrig);
      }
      else {
        scale(_hist_nch, 0.5 / *_sumWTrig);
      }
      scale(_hist_eta, 0.5 / *_sumWTrig);
    }

    /// @}


  private:

    /// @name Counters
    /// @{
    CounterPtr _sumWTrig;
    /// @}

    /// @name Histogram collections
    /// @{
    BinnedHistoPtr<int> _hist_nch;
    Histo1DPtr _hist_eta;
    /// @}

  };



  RIVET_DECLARE_ALIASED_PLUGIN(UA5_1982_I176647, UA5_1982_S875503);

}

Aliases: - UA5_1982_S875503