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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
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Tools/BinnedHistogram.hh"
  4#include "Rivet/Projections/FinalState.hh"
  5#include "Rivet/Projections/UnstableParticles.hh"
  6
  7namespace Rivet {
  8
  9
 10  /// LHCb prompt charm hadron pT and rapidity spectra
 11  class LHCB_2013_I1218996 : public Analysis {
 12  public:
 13
 14    /// @name Constructors etc.
 15    //@{
 16
 17    /// Constructor
 18    LHCB_2013_I1218996()
 19      : Analysis("LHCB_2013_I1218996")
 20    {    }
 21
 22    //@}
 23
 24
 25    /// @name Analysis methods
 26    //@{
 27
 28    /// Book histograms and initialise projections before the run
 29    void init() {
 30
 31      /// Initialise and register projections
 32      declare(UnstableParticles(), "UFS");
 33
 34      /// Book histograms
 35      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add( 2.0, 2.5, book(tmp, 3, 1, 1) );}
 36      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add( 2.5, 3.0, book(tmp, 3, 1, 2) );}
 37      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add( 3.0, 3.5, book(tmp, 3, 1, 3) );}
 38      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add( 3.5, 4.0, book(tmp, 3, 1, 4) );}
 39      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add( 4.0, 4.5, book(tmp, 3, 1, 5) );}
 40
 41      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add( 2.0, 2.5, book(tmp, 2, 1, 1) );}
 42      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add( 2.5, 3.0, book(tmp, 2, 1, 2) );}
 43      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add( 3.0, 3.5, book(tmp, 2, 1, 3) );}
 44      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add( 3.5, 4.0, book(tmp, 2, 1, 4) );}
 45      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add( 4.0, 4.5, book(tmp, 2, 1, 5) );}
 46
 47      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add( 2.0, 2.5, book(tmp, 5, 1, 1) );}
 48      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add( 2.5, 3.0, book(tmp, 5, 1, 2) );}
 49      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add( 3.0, 3.5, book(tmp, 5, 1, 3) );}
 50      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add( 3.5, 4.0, book(tmp, 5, 1, 4) );}
 51      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add( 4.0, 4.5, book(tmp, 5, 1, 5) );}
 52
 53      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add( 2.0, 2.5, book(tmp, 4, 1, 1) );}
 54      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add( 2.5, 3.0, book(tmp, 4, 1, 2) );}
 55      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add( 3.0, 3.5, book(tmp, 4, 1, 3) );}
 56      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add( 3.5, 4.0, book(tmp, 4, 1, 4) );}
 57      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add( 4.0, 4.5, book(tmp, 4, 1, 5) );}
 58
 59      book(_h_pdg4122_Lambdac_pT ,1, 1, 1);
 60    }
 61
 62
 63    /// Perform the per-event analysis
 64    void analyze(const Event& event) {
 65      const double weight = 1.0;
 66
 67      /// @todo Use PrimaryHadrons to avoid double counting and automatically remove the contributions from unstable?
 68      const UnstableParticles &ufs = apply<UnstableParticles> (event, "UFS");
 69      for (const Particle& p : ufs.particles() ) {
 70
 71        // We're only interested in charm hadrons
 72        if (!p.isHadron() || !p.hasCharm()) continue;
 73
 74        // Kinematic acceptance
 75        const double y = p.absrap(); ///< Double analysis efficiency with a "two-sided LHCb"
 76        const double pT = p.pT();
 77
 78        // Fiducial acceptance of the measurements
 79        if (pT > 8.0*GeV || y < 2.0 || y > 4.5) continue;
 80
 81        /// Experimental selection removes non-prompt charm hadrons: we ignore those from b decays
 82        if (p.fromBottom()) continue;
 83
 84        switch (p.abspid()) {
 85        case 411:
 86          _h_pdg411_Dplus_pT_y.fill(y, pT/GeV, weight);
 87          break;
 88        case 421:
 89          _h_pdg421_Dzero_pT_y.fill(y, pT/GeV, weight);
 90          break;
 91        case 431:
 92          _h_pdg431_Dsplus_pT_y.fill(y, pT/GeV, weight);
 93          break;
 94        case 413:
 95          _h_pdg413_Dstarplus_pT_y.fill(y, pT/GeV, weight);
 96          break;
 97        case 4122:
 98          _h_pdg4122_Lambdac_pT->fill(pT/GeV, weight);
 99          break;
100        }
101      }
102
103    }
104
105
106    /// Normalise histograms etc., after the run
107    void finalize() {
108      const double scale_factor = 0.5 * crossSection()/microbarn / sumOfWeights();
109      /// Avoid the implicit division by the bin width in the BinnedHistogram::scale method.
110      for (Histo1DPtr h : _h_pdg411_Dplus_pT_y.histos()) h->scaleW(scale_factor);
111      for (Histo1DPtr h : _h_pdg421_Dzero_pT_y.histos()) h->scaleW(scale_factor);
112      for (Histo1DPtr h : _h_pdg431_Dsplus_pT_y.histos()) h->scaleW(scale_factor);
113      for (Histo1DPtr h : _h_pdg413_Dstarplus_pT_y.histos()) h->scaleW(scale_factor);
114      _h_pdg4122_Lambdac_pT->scaleW(scale_factor);
115    }
116
117    //@}
118
119
120  private:
121
122    /// @name Histograms
123    //@{
124    BinnedHistogram _h_pdg411_Dplus_pT_y;
125    BinnedHistogram _h_pdg421_Dzero_pT_y;
126    BinnedHistogram _h_pdg431_Dsplus_pT_y;
127    BinnedHistogram _h_pdg413_Dstarplus_pT_y;
128    Histo1DPtr _h_pdg4122_Lambdac_pT;
129    //@}
130
131
132  };
133
134
135  // The hook for the plugin system
136  RIVET_DECLARE_PLUGIN(LHCB_2013_I1218996);
137
138}