Rivet analyses

title: ALICE_2017_I1512110

Invariant cross section of neutral pions measured at mid-rapidity in pp collisions at $2.76\,$TeV.

Experiment: ALICE (LHC)

Inspire ID: 1512110

Status: VALIDATED

Authors: none listed

References: none listed

Beams: p+ p+

Beam energies: (1380.0, 1380.0)GeV

Run details: - Transverse momentum spectra of neutral pions and $\eta$ mesons measured at 0.4<p_T<40~GeV/c and 0.6<p_T<20~GeV/c, respectively, and the ratio $\pi^{0}/\eta$, obtained at mid-rapidity in pp collisions at $\sqrt(s) = 2.76\,$TeV with ALICE at the LHC.

Transverse momentum spectra of neutral pions and $\eta$ mesons measured at 0.4<p_T<40~GeV/c and 0.6<p_T<20~GeV/c, respectively, and the ratio $\pi^{0}/\eta$, obtained at mid-rapidity in pp collisions at $\sqrt(s) = 2.76\,$TeV with ALICE at the LHC.

Source code:ALICE_2017_I1512110.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

class ALICE_2017_I1512110 : public Analysis { public:

/// Constructor
ALICE_2017_I1512110()
    : Analysis("ALICE_2017_I1512110"), _rapmax(0.8) { }


void init() {

  const UnstableParticles ufs(Cuts::absrap < _rapmax);
  declare(ufs, "UFS");

  book(_h_pi0, 3, 1, 1);
  book(_h_eta, 4, 1, 1);
  book(_h_etaToPion, 5, 1, 1);

  // temporary plots with the binning of _h_etaToPion
  // to construct the eta/pi0 ratio in the end
  book(_temp_h_pion, "TMP/h_pion", refData(5, 1, 1));
  book(_temp_h_eta, "TMP/h_eta", refData(5, 1, 1));
}


void analyze(const Event& event) {

  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");

  for (const Particle& p : ufs.particles()) {

    if (p.pid() == 111) {
      // neutral pion; ALICE corrects for pi0 feed-down
      if (!(p.hasAncestorWith(Cuts::pid == 310) || p.hasAncestorWith(Cuts::pid == 130) ||  // K0_s, K0_l
            p.hasAncestorWith(Cuts::pid == 321) || p.hasAncestorWith(Cuts::pid == -321) || // K+,K-
            p.hasAncestorWith(Cuts::pid == 3122) || p.hasAncestorWith(Cuts::pid == -3122)
            || // Lambda, Anti-Lambda
            p.hasAncestorWith(Cuts::pid == 3212) || p.hasAncestorWith(Cuts::pid == -3212) || // Sigma0
            p.hasAncestorWith(Cuts::pid == 3222) || p.hasAncestorWith(Cuts::pid == -3222) || // Sigmas
            p.hasAncestorWith(Cuts::pid == 3112) || p.hasAncestorWith(Cuts::pid == -3112) || // Sigmas
            p.hasAncestorWith(Cuts::pid == 3322) || p.hasAncestorWith(Cuts::pid == -3322) || // Cascades
            p.hasAncestorWith(Cuts::pid == 3312) || p.hasAncestorWith(Cuts::pid == -3312)))  // Cascades
      {
        _h_pi0->fill(p.pT() / GeV, 1.0 / (TWOPI * p.pT() / GeV * 2 * _rapmax));
        _temp_h_pion->fill(p.pT() / GeV);
      }
    }
    else if (p.pid() == 221) {
      // eta meson
      _h_eta->fill(p.pT() / GeV, 1.0 / (TWOPI * p.pT() / GeV * 2 * _rapmax));
      _temp_h_eta->fill(p.pT() / GeV);
    }
  }
}


void finalize() {

  scale(_h_pi0, crossSection() / picobarn / sumOfWeights());
  scale(_h_eta, crossSection() / picobarn / sumOfWeights());
  divide(_temp_h_eta, _temp_h_pion, _h_etaToPion);
}

private:

double _rapmax;
Histo1DPtr _h_pi0;
Histo1DPtr _h_eta;
Histo1DPtr _temp_h_pion;
Histo1DPtr _temp_h_eta;
Estimate1DPtr _h_etaToPion;

};

RIVET_DECLARE_PLUGIN(ALICE_2017_I1512110);

} ```