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ALICE_2012_I944757

Measurement of charm production at central rapidity in proton-proton collisions at $\sqrt{s}=7$ TeV
Experiment: ALICE (LHC)
Inspire ID: 944757
Status: VALIDATED
Authors:
  • Marco Giacalone
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Proton Proton events at 7 TeV simulated using PYTHIA 8.240 and HERWIG 7.1.5. SoftQCD:all parameter enabled on the former, while MB (Minimum Bias) and SoftTune snippets were used for the latter.

The $p_\text{T}$-differential inclusive production cross sections of the prompt charmed mesons $D^0$, $D^+$, and $D^{\ast +}$ in the rapidity range $|y|<0.5$ were measured in proton-proton collisions at $\sqrt{s}=7$ TeV at the LHC using the ALICE detector. Reconstructing the decays $D^0 \to K^-\pi^+$, $D^+\to K^-\pi^+\pi^+$, $D^{\ast +} \to D^0\pi^+$, and their charge conjugates, about 8,400 $D^0$, 2,900 $D^+$, and 2,600 $D^{\ast +}$ mesons with $1 < p_\text{T} < 24$ GeV/$c$ were counted, after selection cuts, in a data sample of 3.14$\times 10^8$ events collected with a minimum-bias trigger (integrated luminosity $L_\text{int} = 5$/nb). The results are described within uncertainties by predictions based on perturbative QCD.

Source code: ALICE_2012_I944757.cc
 1#include "Rivet/Analysis.hh"
 2#include "Rivet/Projections/UnstableParticles.hh"
 3
 4namespace Rivet {
 5
 6
 7  /// @brief Charm production at central rapidity in pp at 7 TeV
 8  class ALICE_2012_I944757 : public Analysis {
 9  public:
10
11    /// Constructor
12    RIVET_DEFAULT_ANALYSIS_CTOR(ALICE_2012_I944757);
13
14
15    /// @name Analysis methods
16    /// @{
17
18    /// Book histograms and initialise projections before the run
19    void init() {
20
21      // Initialise and register projections
22      declare(UnstableParticles(Cuts::absrap < 0.5), "UFS");
23
24      // Book histograms
25      book(_h_D0,     1, 1, 1);
26      book(_h_Dplus,  2, 1, 1);
27      book(_h_Dstarp, 3, 1, 1);
28      book(_h_integ,  4, 1, 1);
29
30    }
31
32
33    /// Perform the per-event analysis
34    void analyze(const Event& event) {
35
36        /*PDG code IDs used inside the for loop: 421 = D0, 411 = D+, 413 = D*+ */
37
38        for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
39          if (p.fromBottom())  continue;
40          if (p.abspid() == 421) {
41            _h_D0->fill(p.pT()/GeV);
42            _h_integ->fill(sedges[0]);
43          }
44          else if (p.abspid() == 411) {
45            _h_Dplus->fill(p.pT()/GeV);
46            _h_integ->fill(sedges[1]);
47          }
48          else if (p.abspid()== 413) {
49            _h_Dstarp->fill(p.pT()/GeV);
50            _h_integ->fill(sedges[2]);
51          }
52        }
53    }
54
55
56    /// Normalise histograms etc., after the run
57    void finalize() {
58
59      scale(_h_D0, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
60      scale(_h_Dplus, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
61      scale(_h_Dstarp, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
62      scale(_h_integ, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
63      /* Obtained cross sections data at this point consider both particles and antiparticles
64      hence the added factor 2 in the normalization solves the issue (as done in the paper) */
65    }
66
67    /// @}
68
69
70    /// @name Histograms
71    /// @{
72    Histo1DPtr _h_D0, _h_Dplus, _h_Dstarp;
73    BinnedHistoPtr<string> _h_integ;
74    vector<string> sedges = {"P P --> D0 X", "P P --> D+ X", "P P --> D* X"};
75    /// @}
76
77
78  };
79
80  RIVET_DECLARE_PLUGIN(ALICE_2012_I944757);
81}