Rivet analyses

title: SFM_1984_I196601

Charged multiplicity distribution in $pp$ interactions at CERN ISR energies

Experiment: SFM (CERN ISR)

Inspire ID: 196601

Status: UNVALIDATED

Authors: - Holger Schulz - Andy Buckley

References: - Phys.Rev.D30:528,1984

Beams: p+ p+

Beam energies: (15.2, 15.2); (22.2, 22.2); (26.1, 26.1); (31.1, 31.1)GeV

Run details: - QCD events, double-diffractive events.

WARNING - implemented to the best of abilities, no theory curve in the publication to compare to. Charged multiplicities are measured at $\sqrt{s} = 30.4$, 44.5, 52.2 and 62.2 GeV using a minimum-bias trigger. The data is sub-divided into inelastic as well as non-single-diffractive events.

Source code:SFM_1984_I196601.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/ChargedFinalState.hh"

namespace Rivet {

/// @brief SFM charged multiplicities in NSD and inelastic minbias events class SFM_1984_I196601 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(SFM_1984_I196601);


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

void init() {
  // Projections
  //
  declare(ChargedFinalState(Cuts::absrap < 5 && Cuts::pT > 250 * MeV && Cuts::pT < 3 * GeV), "FS");

  // Histograms
  size_t ih = 1;
  for (double eVal : allowedEnergies()) {
    const string en = toString(round(eVal / MeV));
    if (isCompatibleWithSqrtS(eVal, 1e-2)) _sqs = en;
    book(_h[en + "inel"], 1, 1, ih);
    book(_h[en + "nsd"], 2, 1, ih);
    ++ih;
  }
  raiseBeamErrorIf(_sqs.empty());
}


// Analyse each event
void analyze(const Event& event) {
  const ChargedFinalState& fs = apply<ChargedFinalState>(event, "FS");

  // Trigger
  if (fs.particles().size() < 1) vetoEvent;

  // Event classification:
  int n_left(0), n_right(0), n_large_x(0);
  for (const Particle& p : fs.particles()) {
    // Calculate the particles' Feynman x
    const double x_feyn = 2.0 * fabs(p.pz()) / sqrtS();
    if (x_feyn > 0.8) n_large_x += 1;

    // Pseudorapidity
    const double eta = p.eta();
    if (eta > 0.0)
      n_right += 1;
    else if (eta < 0.0)
      n_left += 1;
  }
  MSG_DEBUG("N_left: " << n_left << ", "
                       << "N_right: " << n_right << ", "
                       << "N_large_x: " << n_large_x);


  // Single diffractive: either one large x particle or 0 particles in the one hemisphere but more than 7 in the other hemisphere
  bool isDiffractive = (n_large_x == 1)
      || (((n_left == 0) && (fs.particles().size() < 7))
          || ((n_right == 0) && (fs.particles().size() < 7)));


  _h[_sqs + "inel"]->fill(fs.particles().size());
  if (!isDiffractive) _h[_sqs + "nsd"]->fill(fs.particles().size());
}


void finalize() {
  normalize(_h);
}

/// @}

private:

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

};

RIVET_DECLARE_ALIASED_PLUGIN(SFM_1984_I196601, SFM_1984_S1178091);

} ```

Aliases: - SFM_1984_S1178091