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Rivet analyses reference
ALICE_2012_I1116147
pT of neutral pions and $\eta$ mesons in $pp$ collisions at $7\,$TeV and $0.9\,$TeV
Experiment: ALICE (LHC)
Inspire ID: 1116147
Status: VALIDATED
Authors:
References:
Beams: p+ p+
Beam energies: (450.0, 450.0); (3500.0, 3500.0) GeV
Run details:
- Generic $pp$ collision events.
Transverse momentum spectra of neutral pions and $\eta$ mesons and the ratio $\pi^0/\eta$, obtained at mid-rapidity in pp collisions at $\sqrt{s} = 7\,$TeV with ALICE at the LHC. The transverse momentum spectrum of neutral pions is also given for $\sqrt{s} = 0.9\,$TeV.
Source code:
ALICE_2012_I1116147.cc
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86 | //-*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
class ALICE_2012_I1116147 : public Analysis {
public:
/// Constructor
DEFAULT_RIVET_ANALYSIS_CTOR(ALICE_2012_I1116147);
/// Initialise projections and histograms
void init() {
const UnstableParticles ufs(Cuts::absrap < RAPMAX);
declare(ufs, "UFS");
// Check if cm energy is 7 TeV or 0.9 TeV
if (fuzzyEquals(sqrtS()/GeV, 900, 1E-3)) _cm_energy_case = 1;
else if (fuzzyEquals(sqrtS()/GeV, 7000, 1E-3)) _cm_energy_case = 2;
if (_cm_energy_case == 0)
throw UserError("Center of mass energy of the given input is neither 900 nor 7000 GeV.");
// Book histos
if (_cm_energy_case == 1) {
book(_h_pi0, 2,1,1);
} else {
book(_h_pi0, 1,1,1);
book(_h_eta, 3,1,1);
book(_h_etaToPion, 4,1,1);
}
// Temporary plots with the binning of _h_etaToPion to construct the eta/pi0 ratio
book(_temp_h_pion, "TMP/h_pion", refData(4,1,1));
book(_temp_h_eta , "TMP/h_eta", refData(4,1,1));
}
/// Per-event analysis
void analyze(const Event& event) {
const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
for (const Particle& p : ufs.particles()) {
const double normfactor = TWOPI*p.pT()/GeV*2*RAPMAX;
if (p.pid() == 111) {
// Neutral pion; ALICE corrects for pi0 feed-down from K_0_s and Lambda
if (p.hasAncestor(310) || p.hasAncestor(3122) || p.hasAncestor(-3122)) continue; //< K_0_s, Lambda, Anti-Lambda
_h_pi0->fill(p.pT()/GeV, 1.0/normfactor);
_temp_h_pion->fill(p.pT()/GeV);
} else if (p.pid() == 221 && _cm_energy_case == 2) {
// eta meson (only for 7 TeV)
_h_eta->fill(p.pT()/GeV, 1.0/normfactor);
_temp_h_eta->fill(p.pT()/GeV);
}
}
}
/// Normalize histos and construct ratio
void finalize() {
scale(_h_pi0, crossSection()/microbarn/sumOfWeights());
if (_cm_energy_case == 2) {
divide(_temp_h_eta, _temp_h_pion, _h_etaToPion);
scale(_h_eta, crossSection()/microbarn/sumOfWeights());
}
}
private:
const double RAPMAX = 0.8;
int _cm_energy_case = 0;
Histo1DPtr _h_pi0, _h_eta;
Histo1DPtr _temp_h_pion, _temp_h_eta;
Scatter2DPtr _h_etaToPion;
};
DECLARE_RIVET_PLUGIN(ALICE_2012_I1116147);
}
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