Rivet Analyses Reference

ALICE_2017_I1511870

Measurement of D-meson production at mid-rapidity in pp collisions at $\sqrt{s}=7$ TeV
Experiment: ALICE (LHC)
Inspire ID: 1511870
Status: VALIDATED
Authors:
  • Marco Giacalone
References:
  • DOI:10.1140/epjc/s10052-017-5090-4
  • arXiv: 1702.00766
Beams: p+ p+
Beam energies: (3500.0, 3500.0) GeV
Run details:
  • Minimum bias events

CERN-LHC. The production cross sections of the prompt charmed mesons $D^0$, $D^+$, $D^{*+}$ and $D_s$ were measured at mid-rapidity in proton-proton collisions at a centre-of-mass energy $\sqrt{s_{NN}}=7$ TeV with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays $D^0\to K\pi, D^+\to K\pi\pi$, $D^{*+} \to D^0\pi \to K\pi\pi$, $D_s \to\phi \pi \to KK\pi $, and their charge conjugates. With respect to previous measurements in the same rapidity region, the coverage in transverse momentum pt is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total c-cbar production cross section is likewise improved. The measured pT-differential cross sections are compared with the results of three perturbative QCD calculations.

Source code: ALICE_2017_I1511870.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief Add a short analysis description here
  class ALICE_2017_I1511870 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(ALICE_2017_I1511870);


    /// @name Analysis methods
    //@{

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

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

      // Book histograms
      book(_h_D0,1, 1, 1);                                      // production cross section of D0 meson
      book(_h_Dplus,2, 1, 1);                                   // production cross section of Dplus meson
      book(_h_Dstar,3, 1, 1);                                   // production cross section of Dstar meson
      book(_h_Ds,4, 1, 1);                                      // production cross section of Ds meson
      book(_h_DplusonD0,5, 1, 1);                               // ratio of production cross section between Dplus and D0
      book(_h_DstaronD0,6, 1, 1);                               // ratio of production cross section between Dstar and D0
      book(_h_DsonD0,7, 1, 1);                                  // ratio of production cross section between Ds and D0
      book(_h_DsonDplus,8, 1, 1);                               // ratio of production cross section between Ds and Dplus
      book(_h_D0int,9,1,1);                                     // pt-integrated production cross section of D0 meson
      book(_h_Dplusint,10,1,1);                                 // pt-integrated production cross section of Dplus meson
      book(_h_Dstarint,11,1,1);                                 // pt-integrated production cross section of Dstar meson
      book(_h_Dsint,12,1,1);                                    // pt-integrated production cross section of Ds meson
      book(_h_cc,13,1,1);                                       // integrated cross section of ccbar
      book(_h_ptd0,14,1,1);                                     // mean pt of prompt D0
      book(_h_D0full,15,1,1);                                   // integrated cross section for D0 in full rapidity
      book(_h_ccfull,16,1,1);                                   // integrated cross section for ccbar in full rapidity
      book(_h_wei,"_h_wei");    				                        // Counter used to calculate D0 mean pt (necessary to store an integer number for event normalisation, i.e. to still be able to compute <pT> from multiple parallel MC jobs)
      book(_h_D0dummy,"TMP/_h_D0dummy",refData(5,1,1));         // used to make DplusonD0
      book(_h_D0dummy1,"TMP/_h_D0dummy1",refData(7,1,1));       // used to make DsonD0
      book(_h_Dplusdummy,"TMP/_h_Dplusdummy",refData(8,1,1));   // used to make DsonDplus
    }


    /// Perform the per-event analysis
    /*PDG code IDs used inside the foreach cycle: 421 = D0, 411 = D+, 413 = D*+, 431 = Ds+ */
    void analyze(const Event& event) {
        const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
        
        for(const Particle& p : ufs.particles()) {
          if(p.abspid() == 421){
              if(not p.fromBottom()){
                  _h_D0full         ->fill(7.000000e+03/GeV);    
                  _h_ccfull         ->fill(7.000000e+03/GeV);}
          }
          if(p.absrap() < 0.5){
            if(p.fromBottom())
                continue;
            else
                {    
                if(p.abspid() == 421){
                    _h_D0           ->fill(p.pT()/GeV); 
                    _h_D0dummy      ->fill(p.pT()/GeV);
                    _h_D0dummy1     ->fill(p.pT()/GeV);
                    _h_D0int        ->fill(7.000000e+03/GeV);
                    _h_cc           ->fill(7.000000e+03/GeV);
                    _h_ptd0         ->fill(7.000000e+03/GeV,p.pT()/GeV);
                    _h_wei          ->fill();
                    }
                else if(p.abspid() == 411){
                    _h_Dplus        ->fill(p.pT()/GeV);
                    _h_Dplusdummy   ->fill(p.pT()/GeV);
                    _h_Dplusint     ->fill(7.000000e+03/GeV); 
                    }
                else if(p.abspid() == 413){
                    _h_Dstar        ->fill(p.pT()/GeV); 
                    _h_Dstarint     ->fill(7.000000e+03/GeV);    
                    }
                else if(p.abspid() == 431){
                    _h_Ds           ->fill(p.pT()/GeV);
                    _h_Dsint        ->fill(7.000000e+03/GeV); 
                }    
                }
        }
        }  
    }            

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

      //normalize(_h_YYYY); // normalize to unity
      //all the histograms are divided by 2 since at this point the results consider both particles and antiparticles
      scale(_h_D0,          crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dplus,       crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dstar,       crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Ds,          crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_D0dummy,     crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_D0dummy1,    crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dplusdummy,  crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      
      divide(_h_Dplus,  _h_D0dummy,     _h_DplusonD0); //ratio plots
      divide(_h_Dstar,  _h_D0dummy,     _h_DstaronD0);
      divide(_h_Ds,     _h_D0dummy1,    _h_DsonD0);
      divide(_h_Ds,     _h_Dplusdummy,  _h_DsonDplus);
      
      scale(_h_D0int,       crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dplusint,    crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dstarint,    crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      scale(_h_Dsint,       crossSection()/(microbarn*2*sumOfWeights())); // norm to cross section
      
      scale(_h_cc,          1.034*crossSection()/(microbarn*2*sumOfWeights()*0.542)); 
            // 0.542 accounts for the fraction of charm quarks hadronizing into D0 mesons, the ALICE uncertainty on such a factor (0.542 ± 0.024) is not propagated here.
            // 1.034 is used to include the correction of the different shapes of the rapidity distributions of D0 and ccbar, the ALICE uncertainty on such a factor (1.034 ± 0.015, i.e. 1.5 percentage point of uncertainty) is not propagated here.
      
      if( _h_wei->effNumEntries()!=0.) scale(_h_ptd0,        1/ _h_wei->val()); //scaled for the number of events used to calculate the mean pT
      
      scale(_h_D0full,      crossSection()/(millibarn*2*sumOfWeights())); 
            // NOTE : for the ALICE data, the y extrapolation from |y|<0.5 to full-y phase space is done with an FONLL-based factor (8.56 +2.51 -0.42). Here in MC we simply use direct MC outcome over full y.
      
      scale(_h_ccfull,      1.034*crossSection()/(millibarn*2*sumOfWeights()*0.542)); 
            // 0.542 accounts for the fraction of charm quarks hadronizing into D0 mesons, the ALICE uncertainty on such a factor (0.542 ± 0.024) is not propagated here.
            // 1.034 is used to include the correction of the different shapes of the rapidity distributions of D0 and ccbar, the ALICE uncertainty on such a factor (1.034 ± 0.016, i.e. 1.5 percentage point of uncertainty) is not propagated here.
    }

    //@}


    /// @name Histograms
    //@{
    CounterPtr _h_wei;
    Histo1DPtr _h_D0, _h_Dplus, _h_Dstar, _h_Ds, _h_D0int, _h_Dplusint, _h_Dstarint, _h_Dsint, _h_cc, _h_D0full, _h_D0dummy, _h_D0dummy1, _h_Dplusdummy , _h_ccfull, _h_ptd0;
    Scatter2DPtr _h_DplusonD0, _h_DstaronD0, _h_DsonD0, _h_DsonDplus;
    //@}


  };


  // The hook for the plugin system
  DECLARE_RIVET_PLUGIN(ALICE_2017_I1511870);


}