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LHCB_2013_I1218996

Charm hadron differential cross-sections in p_\perp and rapidity
Experiment: LHCB (LHC 7TeV)
Inspire ID: 1218996
Status: VALIDATED
Authors:
  • Patrick Spradlin
References: Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Minimum bias QCD events, proton--proton interactions at $\sqrt{s} = 7$ TeV.

Measurements of differential production cross-sections with respect to transverse momentum, $d \sigma(H_c + \mathrm{c.c.}) / d p_T$, for charm hadron species $H_c \in \{ D^0, D^+, D^\ast(2010)^+, D_s^+, \Lambda_c^+ \}$ in proton--proton collisions at center-of-mass energy $\sqrt{s}= 7$ TeV. The differential cross-sections are measured in bins of hadron transverse momentum ($p_T$) and rapidity ($y$) with respect to the beam axis in the region $0 < p_T < 8$ GeV/$c$ and $2.0 < y < 4.5$, where $p_T$ and $y$ are measured in the proton--proton CM frame. In this analysis code, it is assumed that the event coordinate system is in the proton--proton CM frame with the $z$-axis corresponding to the proton--proton collision axis (as usual). Contributions of charm hadrons from the decays of $b$-hadrons and other particles with comparably large mean lifetimes have been removed in the measurement. In this analysis code, this is implemented by counting only charm hadrons that do not have an ancestor that contains a $b$ quark.

Source code: LHCB_2013_I1218996.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableFinalState.hh"

namespace Rivet {


  /// LHCb prompt charm hadron pT and rapidity spectra
  class LHCB_2013_I1218996 : public Analysis {
  public:

    /// @name Constructors etc.
    //@{

    /// Constructor
    LHCB_2013_I1218996()
      : Analysis("LHCB_2013_I1218996")
    {    }

    //@}


    /// @name Analysis methods
    //@{

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

      /// Initialise and register projections
      declare(UnstableFinalState(), "UFS");

      /// Book histograms
      _h_pdg411_Dplus_pT_y.addHistogram(  2.0, 2.5, bookHisto1D(3, 1, 1));
      _h_pdg411_Dplus_pT_y.addHistogram(  2.5, 3.0, bookHisto1D(3, 1, 2));
      _h_pdg411_Dplus_pT_y.addHistogram(  3.0, 3.5, bookHisto1D(3, 1, 3));
      _h_pdg411_Dplus_pT_y.addHistogram(  3.5, 4.0, bookHisto1D(3, 1, 4));
      _h_pdg411_Dplus_pT_y.addHistogram(  4.0, 4.5, bookHisto1D(3, 1, 5));

      _h_pdg421_Dzero_pT_y.addHistogram(  2.0, 2.5, bookHisto1D(2, 1, 1));
      _h_pdg421_Dzero_pT_y.addHistogram(  2.5, 3.0, bookHisto1D(2, 1, 2));
      _h_pdg421_Dzero_pT_y.addHistogram(  3.0, 3.5, bookHisto1D(2, 1, 3));
      _h_pdg421_Dzero_pT_y.addHistogram(  3.5, 4.0, bookHisto1D(2, 1, 4));
      _h_pdg421_Dzero_pT_y.addHistogram(  4.0, 4.5, bookHisto1D(2, 1, 5));

      _h_pdg431_Dsplus_pT_y.addHistogram(  2.0, 2.5, bookHisto1D(5, 1, 1));
      _h_pdg431_Dsplus_pT_y.addHistogram(  2.5, 3.0, bookHisto1D(5, 1, 2));
      _h_pdg431_Dsplus_pT_y.addHistogram(  3.0, 3.5, bookHisto1D(5, 1, 3));
      _h_pdg431_Dsplus_pT_y.addHistogram(  3.5, 4.0, bookHisto1D(5, 1, 4));
      _h_pdg431_Dsplus_pT_y.addHistogram(  4.0, 4.5, bookHisto1D(5, 1, 5));

      _h_pdg413_Dstarplus_pT_y.addHistogram(  2.0, 2.5, bookHisto1D(4, 1, 1));
      _h_pdg413_Dstarplus_pT_y.addHistogram(  2.5, 3.0, bookHisto1D(4, 1, 2));
      _h_pdg413_Dstarplus_pT_y.addHistogram(  3.0, 3.5, bookHisto1D(4, 1, 3));
      _h_pdg413_Dstarplus_pT_y.addHistogram(  3.5, 4.0, bookHisto1D(4, 1, 4));
      _h_pdg413_Dstarplus_pT_y.addHistogram(  4.0, 4.5, bookHisto1D(4, 1, 5));

      _h_pdg4122_Lambdac_pT = bookHisto1D(1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      const double weight = event.weight();

      /// @todo Use PrimaryHadrons to avoid double counting and automatically remove the contributions from unstable?
      const UnstableFinalState &ufs = apply<UnstableFinalState> (event, "UFS");
      foreach (const Particle& p, ufs.particles() ) {

        // We're only interested in charm hadrons
        if (!p.isHadron() || !p.hasCharm()) continue;

        // Kinematic acceptance
        const double y = p.absrap(); ///< Double analysis efficiency with a "two-sided LHCb"
        const double pT = p.pT();

        // Fiducial acceptance of the measurements
        if (pT > 8.0*GeV || y < 2.0 || y > 4.5) continue;

        /// Experimental selection removes non-prompt charm hadrons: we ignore those from b decays
        if (p.fromBottom()) continue;

        switch (p.abspid()) {
        case 411:
          _h_pdg411_Dplus_pT_y.fill(y, pT/GeV, weight);
          break;
        case 421:
          _h_pdg421_Dzero_pT_y.fill(y, pT/GeV, weight);
          break;
        case 431:
          _h_pdg431_Dsplus_pT_y.fill(y, pT/GeV, weight);
          break;
        case 413:
          _h_pdg413_Dstarplus_pT_y.fill(y, pT/GeV, weight);
          break;
        case 4122:
          _h_pdg4122_Lambdac_pT->fill(pT/GeV, weight);
          break;
        }
      }

    }


    /// Normalise histograms etc., after the run
    void finalize() {
      const double scale_factor = 0.5 * crossSection()/microbarn / sumOfWeights();
      /// Avoid the implicit division by the bin width in the BinnedHistogram::scale method.
      foreach (Histo1DPtr h, _h_pdg411_Dplus_pT_y.getHistograms()) h->scaleW(scale_factor);
      foreach (Histo1DPtr h, _h_pdg421_Dzero_pT_y.getHistograms()) h->scaleW(scale_factor);
      foreach (Histo1DPtr h, _h_pdg431_Dsplus_pT_y.getHistograms()) h->scaleW(scale_factor);
      foreach (Histo1DPtr h, _h_pdg413_Dstarplus_pT_y.getHistograms()) h->scaleW(scale_factor);
      _h_pdg4122_Lambdac_pT->scaleW(scale_factor);
    }

    //@}


  private:

    /// @name Histograms
    //@{
    BinnedHistogram<double> _h_pdg411_Dplus_pT_y;
    BinnedHistogram<double> _h_pdg421_Dzero_pT_y;
    BinnedHistogram<double> _h_pdg431_Dsplus_pT_y;
    BinnedHistogram<double> _h_pdg413_Dstarplus_pT_y;
    Histo1DPtr _h_pdg4122_Lambdac_pT;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(LHCB_2013_I1218996);

}