Rivet analyses

title: UA5_1982_I176647

UA5 multiplicity and pseudorapidity distributions for $pp$ and $p\bar{p}$.

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 $p\bar{p}$ beams.

Comparisons of multiplicity and pseudorapidity distributions for $pp$ and $p\bar{p}$ 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++ // -- 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