Rivet analyses

title: HERA_2015_I1353667

Combined H1/ZEUS $D^*$ production cross-sections in DIS

Experiment: H1/ZEUS (HERA)

Inspire ID: 1353667

Status: UNVALIDATED

Authors: - Andy Buckley

References: - JHEP 1509 (2015) 149 - DOI:10.1007/JHEP09(2015)149 - DESY-15-037 - arxiv:1503.06042 - http://www-h1.desy.de/publications/htmlsplit/DESY-15-037.long.poster.html

Beams: p+ e-, p+ e+

Beam energies: (159.0, 159.0)GeV

Run details: - Inclusive DIS events. $Q^2$ cut must be lower than 1.5 $\GeV^2$.

H1 and ZEUS combined differential cross-sections for inclusive $D^{\pm}$ production in deep-inelastic $ep$ scattering at HERA. The cross-sections are combined in the common visible phase-space region of photon virtuality $Q^2 > 5 \GeV^2$, electron inelasticity $0.02 < y < 0.7$, and the $D^{\pm}$ meson's transverse momentum $p_T(D^) > 1.5 \GeV$ and pseudorapidity $|\eta(D^)| < 1.5$. The combination procedure takes into account all correlations. Double-differential cross sections $d2\sigma/dQ^2 dy$ are combined with earlier $D^{*\pm}$ data, extending the kinematic range down to $Q^2 > 1.5 \GeV^2$.

Source code:HERA_2015_I1353667.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DISKinematics.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Combined H1/ZEUS D* production cross-sections in DIS class HERA_2015_I1353667 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(HERA_2015_I1353667);


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

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

  // Initialise and register projections
  // declare(FinalState(Cuts::abseta < 5 && Cuts::pT > 100*MeV), "FS");
  // FinalState fs;
  declare(DISKinematics(), "Kinematics");
  declare(UnstableParticles(), "Dstars");
  //Cuts::abspid == PID::DSTARPLUS

  // Book histograms
  book(_h_pTD, 1, 1, 1);
  book(_h_etaD, 2, 1, 1);
  book(_h_zD, 3, 1, 1);
  book(_h_Q2, 4, 1, 1);
  book(_h_y, 5, 1, 1);
  book(_h_Q2y, 6, 1, 1);
}


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

  // Determine kinematics, including event orientation
  const DISKinematics& kin = apply<DISKinematics>(event, "Kinematics");
  const int orientation = kin.orientation();

  // Q2 and inelasticity cuts
  if (!inRange(kin.Q2(), 1.5 * GeV2, 1000 * GeV2)) vetoEvent;
  if (!inRange(kin.y(), 0.02, 0.7)) vetoEvent;


  // D* reconstruction
  const Particles unstables = apply<ParticleFinder>(event, "Dstars")
                                  .particles(Cuts::pT > 1.5 * GeV && Cuts::abseta < 1.5);
  const Particles dstars = select(unstables,
                                  [](const Particle& p) { return p.abspid() == PID::DSTARPLUS; });
  if (dstars.empty()) vetoEvent;
  MSG_DEBUG("#D* = " << dstars.size());
  const Particle& dstar = dstars.front();
  const double zD = (dstar.E() - orientation * dstar.pz()) / (2 * kin.beamLepton().E() * kin.y());

  // Single-differential histograms with higher low-Q2 cut
  if (kin.Q2() > 5 * GeV2) {
    _h_pTD->fill(dstar.pT() / GeV);
    _h_etaD->fill(orientation * dstar.eta());
    _h_zD->fill(zD / GeV);
    _h_Q2->fill(kin.Q2() / GeV2);
    _h_y->fill(kin.y());
  }

  // // Double-differential (y,Q2) histograms
  // _h_Q2y->fill(kin.Q2()/GeV2, kin.y());
}


/// Normalise histograms etc., after the run
void finalize() {
  const double sf = crossSection() / nanobarn / sumOfWeights();
  scale(_h_pTD, sf);
  scale(_h_etaD, sf);
  scale(_h_zD, sf);
  scale(_h_Q2, sf);
  scale(_h_y, sf);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pTD, _h_etaD, _h_zD, _h_Q2, _h_y;
Histo2DPtr _h_Q2y;
/// @}

};

RIVET_DECLARE_PLUGIN(HERA_2015_I1353667);

} ```