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ALICE_2017_I1620477

Invariant cross section of neutral pions at mid-rapidity in $8\,$TeV pp collisions
Experiment: ALICE (LHC)
Inspire ID: 1620477
Status: VALIDATED
Authors:
  • Hendrik Poppenborg
References:
  • Eur. Phys. J. C (2018) 78: 263
  • 10.1140/epjc/s10052-018-5612-8
  • arXiv: hep-ex/1708.08745
Beams: p+ p+
Beam energies: (4000.0, 4000.0) GeV
    No run details listed

Transverse momentum spectra of neutral pions and $\eta$ mesons measured at $0.3<p_T<35 GeV/c$ and $0.5<p_T<35 GeV/c$, respectively, and the ratio $\pi^{0}/\eta$, obtained at mid-rapidity in $pp$ collisions at $\sqrt(s) = 8\,$TeV with ALICE at the LHC.

Source code: ALICE_2017_I1620477.cc
 1//-*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4#include "Rivet/Tools/ParticleUtils.hh"
 5
 6namespace Rivet {
 7
 8
 9  class ALICE_2017_I1620477 : public Analysis {
10  public:
11
12    /// Constructor
13    ALICE_2017_I1620477()
14      : Analysis("ALICE_2017_I1620477"),
15        _rapmax(0.8)
16    {    }
17
18
19    void init() {
20
21      const UnstableParticles ufs(Cuts::absrap < _rapmax);
22      declare(ufs, "UFS");
23
24      book(_h_pi0,1,1,1);
25      book(_h_eta,2,1,1);
26      book(_h_etaToPion,8,1,1);
27
28      // temporary plots with the binning of _h_etaToPion
29      // to construct the eta/pi0 ratio in the end
30      book(_temp_h_pion,"TMP/h_pion",refData(8,1,1));
31      book(_temp_h_eta, "TMP/h_eta", refData(8,1,1));
32    }
33
34
35    void analyze(const Event& event) {
36
37      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
38
39      for(const Particle& p : ufs.particles()) {
40
41        if (p.pid() == 111) {
42          // neutral pion; ALICE corrects for pi0 feed-down
43          if ( !(p.hasAncestorWith(Cuts::pid == 310)  || p.hasAncestorWith(Cuts::pid == 130)   || // K0_s, K0_l
44                 p.hasAncestorWith(Cuts::pid == 321)  || p.hasAncestorWith(Cuts::pid == -321)  || // K+,K-
45                 p.hasAncestorWith(Cuts::pid == 3122) || p.hasAncestorWith(Cuts::pid == -3122) || // Lambda, Anti-Lambda
46                 p.hasAncestorWith(Cuts::pid == 3212) || p.hasAncestorWith(Cuts::pid == -3212) || // Sigma0
47                 p.hasAncestorWith(Cuts::pid == 3222) || p.hasAncestorWith(Cuts::pid == -3222) || // Sigmas
48                 p.hasAncestorWith(Cuts::pid == 3112) || p.hasAncestorWith(Cuts::pid == -3112) || // Sigmas
49                 p.hasAncestorWith(Cuts::pid == 3322) || p.hasAncestorWith(Cuts::pid == -3322) || // Cascades
50                 p.hasAncestorWith(Cuts::pid == 3312) || p.hasAncestorWith(Cuts::pid == -3312) )) // Cascades
51            {
52              _h_pi0->fill(p.pT()/GeV, 1. /(TWOPI*p.pT()/GeV*2*_rapmax));
53              _temp_h_pion->fill(p.pT()/GeV);
54            }
55        }
56        else if (p.pid() == 221) {
57          // eta meson
58          _h_eta->fill(p.pT()/GeV, 1. /(TWOPI*p.pT()/GeV*2*_rapmax));
59          _temp_h_eta->fill(p.pT()/GeV);
60
61        }
62      }
63    }
64
65
66    void finalize() {
67
68      scale(_h_pi0, crossSection()/picobarn/sumOfWeights());
69      scale(_h_eta, crossSection()/picobarn/sumOfWeights());
70      divide(_temp_h_eta, _temp_h_pion, _h_etaToPion);
71
72    }
73
74
75  private:
76
77    double _rapmax;
78    Histo1DPtr _h_pi0;
79    Histo1DPtr _h_eta;
80    Histo1DPtr _temp_h_pion;
81    Histo1DPtr _temp_h_eta;
82    Estimate1DPtr _h_etaToPion;
83
84  };
85
86
87  RIVET_DECLARE_PLUGIN(ALICE_2017_I1620477);
88
89}