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LHCB_2015_I1396331

Charm hadron differential cross-sections in $p_T$ and rapidity at $\sqrt{s} = 13$ TeV
Experiment: LHCB (LHC 13TeV)
Inspire ID: 1396331
Status: VALIDATED
Authors:
  • Dominik Muller
  • Patrick Spradlin
References:
  • JHEP 1603 (2016) 159 JHEP 1609 (2016) 013 JHEP 1705 (2017) 074
  • doi 10.1007/JHEP09(2016)013 10.1007/JHEP05(2017)074 10.1007/JHEP03(2016)159
  • arXiv 1510.01707 [hep-ex]
  • LHCB-PAPER-2015-041, CERN-PH-EP-2015-272
Beams: p+ p+
Beam energies: (6500.0, 6500.0) GeV
Run details:
  • Minimum bias QCD events, proton--proton interactions at $\sqrt{s} = 13$ 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 $H_c \in \{ D^0, D^+, D^\ast(2010)^+, D_s^+ \}$ in proton--proton collisions at center-of-mass energy $\sqrt{s}= 13$ 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 $0 < p_T < 15$ 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_2015_I1396331.cc
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// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Tools/BinnedHistogram.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

  /// LHCb prompt charm hadron pT and rapidity spectra
  class LHCB_2015_I1396331 : public Analysis {
  public:

    /// Constructor
    DEFAULT_RIVET_ANALYSIS_CTOR(LHCB_2015_I1396331);


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

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

      /// Initialise and register projections
      Cut selection = (Cuts::abspid == 411 || Cuts::abspid == 421 || Cuts::abspid == 431 || Cuts::abspid == 413) \
                       && Cuts::pT < 15.0 && Cuts::absrapIn(2.0, 4.5);
      declare(UnstableParticles(selection), "UPDs");

      /// Book histograms
      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add(2.0, 2.5, book(tmp, 1, 1, 1));}
      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add(2.5, 3.0, book(tmp, 1, 1, 2));}
      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add(3.0, 3.5, book(tmp, 1, 1, 3));}
      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add(3.5, 4.0, book(tmp, 1, 1, 4));}
      {Histo1DPtr tmp; _h_pdg411_Dplus_pT_y.add(4.0, 4.5, book(tmp, 1, 1, 5));}

      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add(2.0, 2.5, book(tmp, 2, 1, 1));}
      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add(2.5, 3.0, book(tmp, 2, 1, 2));}
      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add(3.0, 3.5, book(tmp, 2, 1, 3));}
      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add(3.5, 4.0, book(tmp, 2, 1, 4));}
      {Histo1DPtr tmp; _h_pdg421_Dzero_pT_y.add(4.0, 4.5, book(tmp, 2, 1, 5));}

      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add(2.0, 2.5, book(tmp, 3, 1, 1));}
      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add(2.5, 3.0, book(tmp, 3, 1, 2));}
      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add(3.0, 3.5, book(tmp, 3, 1, 3));}
      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add(3.5, 4.0, book(tmp, 3, 1, 4));}
      {Histo1DPtr tmp; _h_pdg431_Dsplus_pT_y.add(4.0, 4.5, book(tmp, 3, 1, 5));}

      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add(2.0, 2.5, book(tmp, 4, 1, 1));}
      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add(2.5, 3.0, book(tmp, 4, 1, 2));}
      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add(3.0, 3.5, book(tmp, 4, 1, 3));}
      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add(3.5, 4.0, book(tmp, 4, 1, 4));}
      {Histo1DPtr tmp; _h_pdg413_Dstarplus_pT_y.add(4.0, 4.5, book(tmp, 4, 1, 5));}

      // Temporary histos for ratios
      for (int i = 0; i< 5; ++i) {
      	{Histo1DPtr tmp; _hbr_Dzero.add(2.0+i*0.5, 2.5+i*0.5, book(tmp, "/TMP/Dzero"+to_str(i+1), refData(9, 1, 2)));}
      	{Histo1DPtr tmp; _hbr_Dplus.add(2.0+i*0.5, 2.5+i*0.5, book(tmp, "/TMP/Dplus"+to_str(i+1), refData(9, 1, 2)));}
      	{Histo1DPtr tmp; _hbr_Ds.add(2.0+i*0.5, 2.5+i*0.5, book(tmp, "/TMP/Ds"+to_str(i+1), refData(9, 1, 2)));}
      	{Histo1DPtr tmp; _hbr_Dstar.add(2.0+i*0.5, 2.5+i*0.5, book(tmp, "/TMP/Dstar"+to_str(i+1), refData(9, 1, 2)));}
      }

    }


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

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

        if (p.fromBottom()) continue;

        const PdgId apid = p.abspid();
        const double y = p.absrap(); ///< Double analysis efficiency with a "two-sided LHCb"
        const double pT = p.pT()/GeV;

        // select inclusive decay modes
        Particles daus;
        switch (apid) {
        case 411:
          _h_pdg411_Dplus_pT_y.fill(y, pT);
          // veto on decay channel [D+ -> K- pi+ pi+]cc
          if (p.children().size() != 3) break;
          if ( ((p.children(Cuts::pid == -321).size() == 1) && (p.children(Cuts::pid == 211).size() == 2)) ||
          		 ((p.children(Cuts::pid == 321).size() == 1) && (p.children(Cuts::pid == -211).size() == 2)) )
          	_hbr_Dplus.fill(y, pT); // MSG_INFO("Found [ D+ -> K- pi+ pi+ ]cc..."); };
          break;
        case 421:
          _h_pdg421_Dzero_pT_y.fill(y, pT);
          // veto on decay channel [D0 -> K- pi+]cc
          if (p.children().size() != 2) break;
          if ( ((p.children(Cuts::pid == -321).size() == 1) && (p.children(Cuts::pid == 211).size() == 1)) ||
          		 ((p.children(Cuts::pid == 321).size() == 1) && (p.children(Cuts::pid == -211).size() == 1)) )
          	_hbr_Dzero.fill(y, pT); // MSG_INFO("Found [ D0 -> K- pi+ ]cc..."); };

          break;
        case 431:
          _h_pdg431_Dsplus_pT_y.fill(y, pT);
          //veto on decay channel [Ds+ -> [K+ K-]phi0 pi+]cc
          if (p.children().size() != 2) break;
          daus = p.children(Cuts::pid == 333);
          if ( (daus.size() == 1) && (p.children(Cuts::abspid == 211).size() == 1) &&
          		 (daus.front().children(Cuts::abspid ==321).size() == 2) )
          	_hbr_Ds.fill(y, pT); // MSG_INFO("Found [ Ds+ -> phi0(-> K+ K-) pi+ ]cc..."); };
          break;
        case 413:
          _h_pdg413_Dstarplus_pT_y.fill(y, pT);
          // veto on decay channel [D*+ -> [K- pi+]D0 pi+]cc
          if (p.children().size() != 2) break;
          daus = p.children(Cuts::pid == 421);
          if ( (daus.size() == 1) && (p.children(Cuts::abspid == 211).size() == 1) &&
          		( daus.front().children().size() == 2 ) &&
          		( ( (daus.front().children(Cuts::pid == -321).size() == 1 ) && (daus.front().children(Cuts::pid == 211).size() == 1 )	) ||
          		  ( (daus.front().children(Cuts::pid == 321).size() == 1 ) && (daus.front().children(Cuts::pid == -211).size() == 1 ) ) ) )
          	_hbr_Dstar.fill(y, pT); // MSG_INFO("Found [ D*+ -> D0 (-> K- pi+)cc pi+ ]cc..."); };
          break;
        default:
        	break;
        }
      }

    }


    /// Normalise histograms etc., after the run
    void finalize() {
      Histo1DPtr h;
      Histo1DPtr hden;
      /// Factor of 0.5 to correct for the abs(rapidity) used above
      const double scale_factor = 0.5 * crossSection()/microbarn / sumOfWeights();
      /// Avoid the implicit division by the bin width in the BinnedHistogram::scale method.
      for (Histo1DPtr h : _h_pdg411_Dplus_pT_y.histos()) h->scaleW(scale_factor);
      for (Histo1DPtr h : _h_pdg431_Dsplus_pT_y.histos()) h->scaleW(scale_factor);
      for (Histo1DPtr h : _h_pdg413_Dstarplus_pT_y.histos()) h->scaleW(scale_factor);
      for (Histo1DPtr h : _h_pdg421_Dzero_pT_y.histos()) h->scaleW(scale_factor);

      // Do ratios
      for (size_t i = 0; i < 5; ++i) {
      	// book final ratio plots
        book(hr_DplusDzero[i], 9, 1, i+1, true);
        book(hr_DsDzero[i], 10, 1, i+1, true);
        book(hr_DstarDzero[i], 11, 1, i+1, true);
        book(hr_DsDplus[i], 12, 1, i+1, true);
        book(hr_DstarDplus[i], 13, 1, i+1, true);
        book(hr_DsDstar[i], 14, 1, i+1, true);
        // fill ratio plots
      	ratioScatterBins(_hbr_Dplus.histos()[i], _hbr_Dzero.histos()[i], hr_DplusDzero[i]);
      	ratioScatterBins(_hbr_Ds.histos()[i], _hbr_Dzero.histos()[i], hr_DsDzero[i]);
      	ratioScatterBins(_hbr_Dstar.histos()[i], _hbr_Dzero.histos()[i], hr_DstarDzero[i]);
      	ratioScatterBins(_hbr_Ds.histos()[i], _hbr_Dplus.histos()[i], hr_DsDplus[i]);
      	ratioScatterBins(_hbr_Dstar.histos()[i], _hbr_Dplus.histos()[i], hr_DstarDplus[i]);
      	ratioScatterBins(_hbr_Ds.histos()[i], _hbr_Dstar.histos()[i], hr_DsDstar[i]);
      	// scale 100x as measurement is in %
      	hr_DplusDzero[i]->scaleY(100.);
      	hr_DsDzero[i]->scaleY(100.);
      	hr_DstarDzero[i]->scaleY(100.);
      	hr_DsDplus[i]->scaleY(100.);
      	hr_DstarDplus[i]->scaleY(100.);
      	hr_DsDstar[i]->scaleY(100.);
      }
    }

    /// @}


  private:

    // rebin histos to scatter and take ratio
    void ratioScatterBins(Histo1DPtr& hn, Histo1DPtr& hd, Scatter2DPtr &s) {
      vector<double> sedges;
      // extract bin edges from Scatter2D
      for (auto p=s->points().begin(); p != s->points().end(); ++p) {
        sedges.push_back((*p).xMin());
        // MSG_INFO("Scatter2D bin: " << (*p).xMin() << " - " << (*p).xMax());
      }
      sedges.push_back(s->points().back().xMax());
      // make deep-copies as rebinning changes bins each time - any smarter alternative ?!
      Histo1D *hnc, *hdc;
      hnc = new YODA::Histo1D(hn->bins(), hn->totalDbn(), hn->underflow(), hn->overflow());
      hdc = new YODA::Histo1D(hd->bins(), hd->totalDbn(), hd->underflow(), hd->overflow());
      hnc->rebinTo(sedges);
      hdc->rebinTo(sedges);
      divide(*hnc, *hdc, s);
      delete hnc; delete hdc;
    }


    /// @name Histograms
    /// @{
    BinnedHistogram _h_pdg411_Dplus_pT_y, _hbr_Dplus;
    BinnedHistogram _h_pdg421_Dzero_pT_y, _hbr_Dzero;
    BinnedHistogram _h_pdg431_Dsplus_pT_y, _hbr_Ds;
    BinnedHistogram _h_pdg413_Dstarplus_pT_y, _hbr_Dstar;
    Scatter2DPtr hr_DplusDzero[5];
    Scatter2DPtr hr_DsDzero[5];
    Scatter2DPtr hr_DstarDzero[5];
    Scatter2DPtr hr_DsDplus[5];
    Scatter2DPtr hr_DstarDplus[5];
    Scatter2DPtr hr_DsDstar[5];
    /// @}

  };


  DECLARE_RIVET_PLUGIN(LHCB_2015_I1396331);

}