Rivet analyses

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: - DOI: 10.1007/JHEP01(2012)128 - arXiv: 1111.1553

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_T-differential inclusive production cross sections of the prompt charmed mesons D⁰, D⁺, and D^*+ 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 D⁰ → K⁻π⁺, D⁺ → K⁻π⁺π⁺, D^*+ → D⁰π⁺, and their charge conjugates, about 8,400 D⁰, 2,900 D⁺, and 2,600 D^*+ mesons with 1 < p_T < 24 GeV/c were counted, after selection cuts, in a data sample of 3.14×10⁸ events collected with a minimum-bias trigger (integrated luminosity L_int = 5/nb). The results are described within uncertainties by predictions based on perturbative QCD.

Source code:`ALICE_2012_I944757.cc`

#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(sedges[0]);
          }
          else if (p.abspid() == 411) {
            _h_Dplus->fill(p.pT()/GeV);
            _h_integ->fill(sedges[1]);
          }
          else if (p.abspid()== 413) {
            _h_Dstarp->fill(p.pT()/GeV);
            _h_integ->fill(sedges[2]);
          }
        }
    }


    /// 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;
    BinnedHistoPtr<string> _h_integ;
    vector<string> sedges = {"P P --> D0 X", "P P --> D+ X", "P P --> D* X"};
    /// @}


  };

  RIVET_DECLARE_PLUGIN(ALICE_2012_I944757);
}

Rivet analyses

Measurement of charm production at central rapidity in proton-proton collisions at $\sqrt{s}=7$ TeV

Source code:ALICE_2012_I944757.cc

Source code:`ALICE_2012_I944757.cc`