Rivet Analyses Reference

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
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#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Charm production at central rapidity in pp at 7 TeV
  class ALICE_2012_I944757 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ALICE_2012_I944757);


    /// @name Analysis methods
    //@{

    /// Book histograms and initialise projections before the run
    void init() {

      // Initialise and register projections
      declare(UnstableParticles(Cuts::absrap < 0.5), "UFS");

      // Book histograms
      book(_h_D0,     1, 1, 1);
      book(_h_Dplus,  2, 1, 1);
      book(_h_Dstarp, 3, 1, 1);
      book(_h_integ,  4, 1, 1);

    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {

        /*PDG code IDs used inside the for loop: 421 = D0, 411 = D+, 413 = D*+ */

        for (const Particle& p : apply<UnstableParticles>(event, "UFS").particles()) {
          if (p.fromBottom())  continue;
          if (p.abspid() == 421) {
            _h_D0->fill(p.pT()/GeV);
            _h_integ->fill(1);
          }
          else if (p.abspid() == 411) {
            _h_Dplus->fill(p.pT()/GeV);
            _h_integ->fill(2);
          }
          else if (p.abspid()== 413) {
            _h_Dstarp->fill(p.pT()/GeV);
            _h_integ->fill(3);
          }
        }
    }


    /// Normalise histograms etc., after the run
    void finalize() {

      scale(_h_D0, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dplus, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dstarp, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_integ, crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      /* Obtained cross sections data at this point consider both particles and antiparticles
      hence the added factor 2 in the normalization solves the issue (as done in the paper) */
    }

    //@}


    /// @name Histograms
    //@{
    Histo1DPtr _h_D0, _h_Dplus, _h_Dstarp, _h_integ;
    //@}


  };

  // The hook for the plugin system
  RIVET_DECLARE_PLUGIN(ALICE_2012_I944757);
}

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