Rivet analyses

title: LHCB_2011_I891233

Differential cross sections for $J/\psi$ production at 7 TeV

Experiment: LHCB (LHC)

Inspire ID: 891233

Status: VALIDATED

Authors: - Peter Richardson

References: - Eur.Phys.J.C 71 (2011) 1645

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - hadronic events with Jpsi production

Measurement of the double differential (in $p_\perp$ and $y$) cross section for $J/\psi$ production at 7 TeV by the LHCB collaboration.

Source code:LHCB_2011_I891233.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief J/psi production at 7 TeV class LHCB_2011_I891233 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2011_I891233);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(), "UFS");
  for (unsigned int ix = 0; ix < 5; ++ix) {
    book(_h_Jpsi[ix], {2.0, 2.5, 3.0, 3.5, 4.0, 4.5});
    for (unsigned int iy = 0; iy < 5; ++iy) {
      if (ix < 4)
        book(_h_Jpsi[ix]->bin(iy + 1), 6 + ix, 1, iy + 1);
      else
        book(_h_Jpsi[ix]->bin(iy + 1), "TMP/JPsi_" + toString(iy), refData(6, 1, iy + 1));
    }
  }
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  // Final state of unstable particles to get particle spectra
  const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
  // J/psi
  for (const Particle& p : ufs.particles(Cuts::pid == 443)) {
    // prompt/non-prompt
    bool nonPrompt = p.fromBottom();
    double absrap = p.absrap();
    double xp = p.perp();
    if (absrap < 2. || absrap > 4.5 || xp > 14.) continue;
    _h_Jpsi[4]->fill(absrap, xp);
    if (nonPrompt) {
      _h_Jpsi[1]->fill(absrap, xp);
    }
    else {
      _h_Jpsi[0]->fill(absrap, xp);
      _h_Jpsi[2]->fill(absrap, xp);
      _h_Jpsi[3]->fill(absrap, xp);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // 1/2 due rapidity folding +/-
  double factor = 0.5 * crossSection() / nanobarn / sumOfWeights();
  for (unsigned int ix = 0; ix < 5; ++ix) {
    scale(_h_Jpsi[ix], factor);
    divByGroupWidth(_h_Jpsi[ix]);
  }
  for (unsigned int ix = 0; ix < _h_Jpsi[4]->numBins(); ++ix) {
    Estimate1DPtr tmp;
    book(tmp, 10, 1, ix + 1);
    divide(_h_Jpsi[1]->bin(ix + 1), _h_Jpsi[4]->bin(ix + 1), tmp);
    tmp->scale(100.);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DGroupPtr _h_Jpsi[5];
/// @}

};

RIVET_DECLARE_PLUGIN(LHCB_2011_I891233);

} ```