Rivet analyses

title: NA49_2009_I818217

Inclusive production of protons, anti-protons and neutrons in p+p collisions at 158 GeV/c beam momentum

Experiment: NA49 (SPS)

Inspire ID: 818217

Status: UNVALIDATED

Authors: - Viktar Kireyeu

References: - https://link.springer.com/article/10.1140/epjc/s10052-009-1172-2

Beams: p+ p+

Beam energies: (8.7, 8.7)GeV

Run details: - $pp$ collisions at 17.3~GeV. Minimum bias events.

Production of $p$, $\bar{p}$ and neutrons in fixed target, $p_{\mathrm{lab}} = $158 GeV/c. The elastic trigger is implemented by looking for elastic final states with only 2 particles, instead of attempting to reproduce the experimental trigger, which cannot be directly unfolded.

Source code:NA49_2009_I818217.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Particle.hh"

include "Rivet/Projections/FinalState.hh"

namespace Rivet {

class NA49_2009_I818217 : public Analysis { public:

/// @name Constructors etc.
/// @{
/// Constructor
NA49_2009_I818217()
    : Analysis("NA49_2009_I818217") { }

void init() {
  declare(FinalState(), "FS");
  book(_h_dndxf, 1, 1, 1);
  book(_p_mptxf, 2, 1, 1);
  book(_h_dndy, 3, 1, 1);
  book(_c_ninel, "nInelastic");
}

void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  const size_t numParticles = fs.particles().size();
  const float SRT = event.sqrtS();

  // Inelastic events selection
  if (numParticles <= 2) {
    MSG_DEBUG("Elastic event");
    vetoEvent;
  }
  _c_ninel->fill();

  // Plot distributions
  for (const Particle& p : fs.particles()) {
    if (p.pid() == PID::PROTON) {
      double xF = p.pz() / (SRT / 2.);
      _h_dndxf->fill(xF);
      _h_dndy->fill(p.rapidity());
      _p_mptxf->fill(xF, p.pt());
    }
  }
}

void finalize() {
  scale(_h_dndxf, 1. / *_c_ninel);                            // Scale by the number of inelastic events
  for (auto& b : _h_dndxf->bins()) b.scaleW(1. / b.xWidth()); // Scale by the bin width (dxF)

  scale(_h_dndy, 1. / *_c_ninel);
  for (auto& by : _h_dndy->bins()) by.scaleW(1. / by.xWidth());
}

private:

CounterPtr _c_ninel;   // Counter of inelastic events
Histo1DPtr _h_dndxf;   // dn/dxf histogram
Histo1DPtr _h_dndy;    // dn/dy histogram
Profile1DPtr _p_mptxf; // mean pT vs xF profile

};

RIVET_DECLARE_PLUGIN(NA49_2009_I818217); } ```