Rivet analyses

title: 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: - Nucl.Phys. B871 (2013) 1-20 - DOI: 10.1016/j.nuclphysb.2013.02.010 - arXiv: 1302.2864 - LHCB-PAPER-2012-041, CERN-PH-EP-2013-009

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

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

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

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

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2013_I1218996);

/// @}


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

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

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

  /// Book histograms
  book(_h_pdg421_Dzero_pT_y, {2., 2.5, 3., 3.5, 4., 4.5});
  book(_h_pdg411_Dplus_pT_y, {2., 2.5, 3., 3.5, 4., 4.5});
  book(_h_pdg413_Dstarplus_pT_y, {2., 2.5, 3., 3.5, 4., 4.5});
  book(_h_pdg431_Dsplus_pT_y, {2., 2.5, 3., 3.5, 4., 4.5});
  for (size_t i = 1; i < _h_pdg421_Dzero_pT_y->numBins() + 1; ++i) {
    size_t y = _h_pdg421_Dzero_pT_y->bin(i).index();
    book(_h_pdg421_Dzero_pT_y->bin(i), 2, 1, y);
    book(_h_pdg411_Dplus_pT_y->bin(i), 3, 1, y);
    book(_h_pdg413_Dstarplus_pT_y->bin(i), 4, 1, y);
    book(_h_pdg431_Dsplus_pT_y->bin(i), 5, 1, y);
  }
  book(_h_pdg4122_Lambdac_pT, 1, 1, 1);
}


/// 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, "UFS");
  for (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); break;
      case 421: _h_pdg421_Dzero_pT_y->fill(y, pT / GeV); break;
      case 431: _h_pdg431_Dsplus_pT_y->fill(y, pT / GeV); break;
      case 413: _h_pdg413_Dstarplus_pT_y->fill(y, pT / GeV); break;
      case 4122: _h_pdg4122_Lambdac_pT->fill(pT / GeV); break;
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  const double scale_factor = 0.5 * crossSection() / microbarn / sumOfWeights();
  scale(_h_pdg411_Dplus_pT_y, scale_factor);
  scale(_h_pdg421_Dzero_pT_y, scale_factor);
  scale(_h_pdg431_Dsplus_pT_y, scale_factor);
  scale(_h_pdg413_Dstarplus_pT_y, scale_factor);
  _h_pdg4122_Lambdac_pT->scaleW(scale_factor);
}

/// @}

private:

/// @name Histograms
/// @{
Histo1DGroupPtr _h_pdg411_Dplus_pT_y;
Histo1DGroupPtr _h_pdg421_Dzero_pT_y;
Histo1DGroupPtr _h_pdg431_Dsplus_pT_y;
Histo1DGroupPtr _h_pdg413_Dstarplus_pT_y;
Histo1DPtr _h_pdg4122_Lambdac_pT;
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2013_I1218996);

} ```