Rivet analyses

title: ZEUS_2008_I810112

Measurement of $D^{\pm}$ and $D^0$ production in deep inelastic scattering using a lifetime tag at HERA

Experiment: ZEUS (HERA)

Inspire ID: 810112

Status: VALIDATED

Authors: - Andrii Verbytskyi

References: - Eur.Phys.J.C 63 (2009) 171-188 - DOI:10.1140/epjc/s10052-009-1088-x - arXiv: 0812.3775

Beams: e+ p+, p+ e+, e- p+, p+ e-

Beam energies: ANY

Run details: - Inclusive DIS

The production of $D^{\pm}$ and $D^{0}$ mesons has been measured with the ZEUS detector at HERA using an integrated luminosity of $133.6 pb^{-1}$. The measurements cover the kinematic range $5 < Q^2 < 1000 GeV^2$, $0.02 < y < 0.7$, $1.5 < p_T^D < 15 GeV$ and $\eta^D < 1.6$. Combinatorial background to the D meson signals is reduced by using the ZEUS microvertex detector to reconstruct displaced secondary vertices. Production cross sections are compared with the predictions of next-to-leading-order QCD which is found to describe the data well. Measurements are extrapolated to the full kinematic phase space in order to obtain the open-charm contribution, $F_2^c\bar{c}$, to the proton structure function, $F_2$.

Source code:ZEUS_2008_I810112.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DISFinalState.hh"

include "Rivet/Projections/FastJets.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Measurement of $D^{\pm}$ and $D^0$ production in deep inelastic scattering using a lifetime tag at HERA /// /// @author Andrii Verbytskyi class ZEUS_2008_I810112 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ZEUS_2008_I810112);

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

/// Book histograms and initialise projections before the run
void init() {
  /// Initialise and register projections
  FinalState fs;
  const DISKinematics& diskin = DISKinematics();
  declare(diskin, "Kinematics");
  declare(UnstableParticles(), "UPS");

  book(_h_Dp_q2, 3, 1, 1);
  book(_h_Dp_x, 4, 1, 1);
  book(_h_Dp_pt, 5, 1, 1);
  book(_h_Dp_eta, 6, 1, 1);

  book(_h_Dp_yinq2[0], "TMP/Dp0", refData(11, 1, 1));
  book(_h_Dp_yinq2[1], "TMP/Dp1", refData(11, 1, 2));
  book(_h_Dp_yinq2[2], "TMP/Dp2", refData(11, 1, 3));

  book(_s_Dp_yinq2[0], 11, 1, 1);
  book(_s_Dp_yinq2[1], 11, 1, 2);
  book(_s_Dp_yinq2[2], 11, 1, 3);

  book(_h_D0_q2, 7, 1, 1);
  book(_h_D0_x, 8, 1, 1);
  book(_h_D0_pt, 9, 1, 1);
  book(_h_D0_eta, 10, 1, 1);

  book(_h_D0_yinq2[0], "TMP/D00", refData(12, 1, 1));
  book(_h_D0_yinq2[1], "TMP/D01", refData(12, 1, 2));
  book(_h_D0_yinq2[2], "TMP/D02", refData(12, 1, 3));

  book(_s_D0_yinq2[0], 12, 1, 1);
  book(_s_D0_yinq2[1], 12, 1, 2);
  book(_s_D0_yinq2[2], 12, 1, 3);
}


/// A routine that selects the bin in kinematic space
int _getbinQ2_OK(const DISKinematics& dk) {
  if (inRange(dk.Q2() / GeV2, 5.0, 9.0)) return 0;
  if (inRange(dk.Q2() / GeV2, 9.0, 44.0)) return 1;
  if (inRange(dk.Q2() / GeV2, 44.0, 1000.0)) return 2;
  return -1;
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  /// DIS kinematics
  const DISKinematics& dk = apply<DISKinematics>(event, "Kinematics");
  double q2 = dk.Q2();
  double x = dk.x();
  double y = dk.y();

  ///Assure the event falls into the kinematic range of the measurement.
  if (!inRange(q2 / GeV2, 5, 1000)) vetoEvent;
  if (!inRange(y, 0.02, 0.7)) vetoEvent;

  /// Find out in which bin the measurement falls.
  int bin = _getbinQ2_OK(dk);
  if (bin < 0) vetoEvent;

  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UPS");

  /// Get \f$D^0$\f particles
  for (const Particle& p : select(ufs.particles(), Cuts::abspid == PID::D0)) {
    ///But not from \f$D^{*\pm}$\f decays
    if (p.hasAncestorWith(Cuts::pid == PID::DSTARPLUS)) continue;
    if (p.hasAncestorWith(Cuts::pid == PID::DSTARMINUS)) continue;
    /// Select particles only in the \f$\eta-p_{T}$\f region
    if (!inRange(p.eta(), -1.6, 1.6)) continue;
    if (!inRange(p.pt() / GeV, 1.5, 15.0)) continue;
    /// Fill the general histograms
    _h_D0_pt->fill(p.pt() / GeV);
    _h_D0_eta->fill(p.eta());
    _h_D0_q2->fill(q2 / GeV2);
    _h_D0_x->fill(x);
    /// Fill the cross-sections in selected kinematic bins
    _h_D0_yinq2[bin]->fill(y);
  }

  /// Get \f$D^{\pm}$\f particles
  for (const Particle& p : select(ufs.particles(), Cuts::abspid == PID::DPLUS)) {
    /// Select particles only in the \f$\eta-p_{T}$\f region
    if (!inRange(p.eta(), -1.6, 1.6)) continue;
    if (!inRange(p.pt() / GeV, 1.5, 15.0)) continue;
    /// Fill the general histograms
    _h_Dp_pt->fill(p.pt() / GeV);
    _h_Dp_eta->fill(p.eta());
    _h_Dp_q2->fill(q2 / GeV2);
    _h_Dp_x->fill(x);
    /// Fill the cross-sections in selected kinematic bins
    _h_Dp_yinq2[bin]->fill(y);
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  const double sf = crossSection() / nanobarn / sumOfWeights();
  /// For CS comparison the MC should be corrected to difference between BR used for data and in MC
  scale(_h_Dp_pt, sf);
  scale(_h_Dp_eta, sf);
  scale(_h_Dp_q2, sf);
  scale(_h_Dp_x, sf);

  for (size_t i = 0; i < 3; i++) {
    scale(_h_Dp_yinq2[i], sf);
    barchart(_h_Dp_yinq2[i], _s_Dp_yinq2[i]);
  }

  scale(_h_D0_pt, sf);
  scale(_h_D0_eta, sf);
  scale(_h_D0_q2, sf);
  scale(_h_D0_x, sf);

  for (size_t i = 0; i < 3; i++) {
    scale(_h_D0_yinq2[i], sf);
    barchart(_h_D0_yinq2[i], _s_D0_yinq2[i]);
  }
}

/// @}

private:

Histo1DPtr _h_D0_pt, _h_D0_eta, _h_D0_q2, _h_D0_x, _h_D0_yinq2[3];
Histo1DPtr _h_Dp_pt, _h_Dp_eta, _h_Dp_q2, _h_Dp_x, _h_Dp_yinq2[3];

Estimate1DPtr _s_Dp_yinq2[3];
Estimate1DPtr _s_D0_yinq2[3];

};

RIVET_DECLARE_PLUGIN(ZEUS_2008_I810112);

} ```