Rivet analyses

title: ATLAS_2014_I1292798

$\chi_{c1}$ and $\chi_{c2}$ production at 7 TeV

Experiment: ATLAS (LHC)

Inspire ID: 1292798

Status: VALIDATED

Authors: - Peter Richardson

References: - JHEP 07 (2014) 154, 2014 - Expt page: ATLAS-BPHY-2013-05 - arXiv: 1404.7035

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - chi_C production

Differential cross section for the production of $\chi_{c1}$ and $\chi_{c2}$ production using their decay to J/$\psi$ and a photon.

Source code:ATLAS_2014_I1292798.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief chi_c production at 7 TeV class ATLAS_2014_I1292798 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(ATLAS_2014_I1292798);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(Cuts::pid == 443 || Cuts::pid == 20443 || Cuts::pid == 445), "UFS");
  for (unsigned int ichi = 0; ichi < 2; ++ichi) {
    for (unsigned int ipT = 0; ipT < 2; ++ipT) {
      for (unsigned int iprompt = 0; iprompt < 2; ++iprompt) {
        book(_h_pT[ichi][iprompt][ipT], 1 + ichi + 2 * iprompt + 4 * ipT, 1, 1);
      }
      book(_h_pT[ichi][2][ipT], "TMP/chi_" + toString(ichi) + "_" + toString(ipT),
           refData(1 + ichi + 4 * ipT, 1, 1));
    }
  }
  for (unsigned int iprompt = 0; iprompt < 2; ++iprompt) {
    for (unsigned int ifeed = 0; ifeed < 2; ++ifeed) {
      book(_h_Jpsi[iprompt][ifeed], "TMP/jpsi_" + toString(iprompt) + "_" + toString(ifeed),
           refData(9 + iprompt, 1, 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");

  for (const Particle& p : ufs.particles()) {
    // prompt/non-prompt
    bool nonPrompt = p.fromBottom();
    // J/psi as a reference
    if (p.pid() == 443) {
      if (p.absrap() < 0.75) _h_Jpsi[nonPrompt][0]->fill(p.perp());
    }
    else if (p.children().size() == 2) {
      Particle Jpsi;
      if (p.children()[0].pid() == 22 && p.children()[1].pid() == 443) {
        Jpsi = p.children()[1];
      }
      else if (p.children()[1].pid() == 22 && p.children()[0].pid() == 443) {
        Jpsi = p.children()[0];
      }
      else
        continue;
      if (Jpsi.absrap() > 0.75) continue;
      unsigned int ichi = p.pid() == 20443 ? 0 : 1;
      _h_Jpsi[nonPrompt][1]->fill(Jpsi.perp());
      _h_pT[ichi][nonPrompt][0]->fill(Jpsi.perp());
      _h_pT[ichi][nonPrompt][1]->fill(p.perp());
      _h_pT[ichi][2][0]->fill(Jpsi.perp());
      _h_pT[ichi][2][1]->fill(p.perp());
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // J/psi -> mu+mu- branching ratio
  const double br = 0.05961;
  const double fact = br * crossSection() / picobarn / sumOfWeights();
  for (unsigned int iprompt = 0; iprompt < 3; ++iprompt) {
    for (unsigned int ichi = 0; ichi < 2; ++ichi) {
      for (unsigned int ipT = 0; ipT < 2; ++ipT) {
        scale(_h_pT[ichi][iprompt][ipT], fact);
      }
    }
  }
  for (unsigned int iprompt = 0; iprompt < 2; ++iprompt) {
    for (unsigned int ifeed = 0; ifeed < 2; ++ifeed) {
      scale(_h_Jpsi[iprompt][ifeed], fact);
    }
  }
  // Jpsi feed down prompt
  Estimate1DPtr tmp;
  book(tmp, 9, 1, 1);
  efficiency(_h_Jpsi[0][1], _h_Jpsi[0][0], tmp);
  // ratio prompt chi2/chi1
  book(tmp, 10, 1, 1);
  divide(_h_pT[1][0][0], _h_pT[0][0][0], tmp);
  // ratio non-prompt chi2/chi1
  book(tmp, 11, 1, 1);
  divide(_h_pT[1][1][0], _h_pT[0][1][0], tmp);
  // ratio non-prmopt chi1
  book(tmp, 12, 1, 1);
  divide(_h_pT[0][1][1], _h_pT[0][2][1], tmp);
  // ratio non-prmopt chi2
  book(tmp, 13, 1, 1);
  divide(_h_pT[1][1][1], _h_pT[1][2][1], tmp);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_pT[2][3][2], _h_Jpsi[2][2];
/// @}

};

RIVET_DECLARE_PLUGIN(ATLAS_2014_I1292798);

} ```