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ALICE_2022_I1868463

$\Sigma_c^{0,+,++}$ and $\Lambda_c$ from $\Sigma_c^{0,+,++}$ analysis
Experiment: ALICE (LHC)
Inspire ID: 1868463
Status: VALIDATED
Authors:
  • Marco Giacalone
References:
  • Phys.Rev.Lett. 128 (2022) 012001, 2022
  • DOI:10.1103/PhysRevLett.128.012001
  • arXiv: 2106.08278
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • Minimum bias events

The $p_\mathrm{T}$-differential production cross sections of prompt ${\rm D^{0}}$, ${\rm \Lambda_{c}^{+}}$, and ${\rm \Sigma_{c}^{0,++}}(2455)$ charmed hadrons are measured at midrapidity ($|y|<0.5$) in pp collisions at $\sqrt{s}=13$ TeV. This is the first measurement of ${\rm \Sigma_{c}^{0,++}}$ production in hadronic collisions. Assuming the same production yield for the three $\rm \Sigma_{c}^{0,+,++}$ isospin states, the baryon-to-meson cross section ratios $\rm \Sigma_{c}^{0,+,++}/\rm D^{0}$ and $\rm \Lambda_{c}^{+}/\rm D^{0}$ are calculated in the transverse momentum ($p_{\rm T}$) intervals $2<p_{\rm T}<12$ GeV/$c$ and $1<p_{\rm T}<24$ GeV/$c$. Values significantly larger than in $\rm e^{+}e^{-}$ collisions are observed, indicating for the first time that baryon enhancement in hadronic collisions also extends to the $\mathrm{\Sigma_{c}}$. The feed-down contribution to $\rm \Lambda_{c}^{+}$ production from $\rm \Sigma_{c}^{0,+,++}$ is also reported and is found to be larger than in $\rm e^{+}e^{-}$ collisions. The data are compared with predictions from event generators and other phenomenological models, providing a sensitive test of the different charm-hadronisation mechanisms implemented in the models.

Source code: ALICE_2022_I1868463.cc 
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"


namespace Rivet {


  /// @brief Measurement of prompt charm hadrons production in proton-proton Collisions at 13 TeV
  class ALICE_2022_I1868463 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(ALICE_2022_I1868463);


    /// @name Analysis methods
    ///@{

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

      // Initialise and register projections

      // The basic final-state projection:
      // all final-state particles within
      // the given eta acceptance
      const UnstableParticles up(Cuts::absrap < 0.5);
      declare(up, "up");  

      book(_h_D0,1,1,1);
      book(_h_Lc,2,1,1);
      book(_h_Sc,3,1,1);
      book(_h_LcfromSc,4,1,1);
      book(_h_LcD0,5,1,1);
      book(_h_ScD0,6,1,1);
      book(_h_LcfromScLc,7,1,1);
      book(_h_D04Sc,"TMP/D04Sc",refData(3,1,1));
      book(_h_Lc4Ratio, "TMP/Lc4Ratio", refData(4,1,1));

    }


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

      const UnstableParticles& up = apply<UnstableParticles>(event, "up");
      
      for (const Particle& p : up.particles()) {
        if(p.fromBottom())
          continue;
        else{
          if(p.abspid()==4222 || p.abspid()==4212 || p.abspid()==4112)
            _h_Sc->fill(p.pT()/GeV);
          else if(p.abspid()==4122){
            _h_Lc->fill(p.pT()/GeV);
            _h_Lc4Ratio->fill(p.pT()/GeV);
            if(p.hasAncestor(4222) || p.hasAncestor(4212) || p.hasAncestor(4112) || p.hasAncestor(-4222) || p.hasAncestor(-4212) || p.hasAncestor(-4112))
              _h_LcfromSc->fill(p.pT()/GeV);
          }
          else if(p.abspid()==421){
            _h_D0->fill(p.pT()/GeV);
            _h_D04Sc->fill(p.pT()/GeV);
          }
        }    
      }      
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      
      scale(_h_D0,              crossSection()/(microbarn*2*sumOfWeights()));
      scale(_h_Lc,              crossSection()/(microbarn*2*sumOfWeights()));
      scale(_h_LcfromSc,        crossSection()/(microbarn*2*sumOfWeights()));
      scale(_h_Lc4Ratio,        crossSection()/(microbarn*2*sumOfWeights()));
      scale(_h_Sc,              crossSection()/(microbarn*2*sumOfWeights())); 
      scale(_h_D04Sc,           crossSection()/(microbarn*2*sumOfWeights())); // norm to generated cross-section in pb (after cuts)
      divide(_h_Sc, _h_D04Sc, _h_ScD0);
      divide(_h_Lc, _h_D0, _h_LcD0);
      divide(_h_LcfromSc, _h_Lc4Ratio, _h_LcfromScLc);

    }

    ///@}


    /// @name Histograms
    ///@{
    Histo1DPtr _h_Sc, _h_D0, _h_D04Sc, _h_LcfromSc, _h_Lc , _h_Lc4Ratio;
    Scatter2DPtr _h_LcD0, _h_ScD0, _h_LcfromScLc;
    ///@}


  };


  RIVET_DECLARE_PLUGIN(ALICE_2022_I1868463);

}