Rivet analyses

title: CMS_2012_I1113442

$\Lambda_b$ production at 7 TeV

Experiment: CMS (LHC)

Inspire ID: 1113442

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Lett.B 714 (2012) 136-157 - arXiv: 1205.0594 - Expt page: CMS-BPH-11-007

Beams: p+ p+

Beam energies: (3500.0, 3500.0)GeV

Run details: - hadronic events with Lambda_b meson

Measurement of the cross section for $\Lambda_b$ production at 7 TeV at TeV. The ratio of $\bar{\Lambda}_b$ to $\Lambda_b$ production is also measured.

Source code:CMS_2012_I1113442.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief Lambda_b at 7 TeV class CMS_2012_I1113442 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CMS_2012_I1113442);


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

/// Book histograms and initialise projections before the run
void init() {
  declare(UnstableParticles(), "UFS");
  // histograms
  book(_h_lam, 1, 1, 1);
  book(_h_bar, "TMP/bar_total", refData<YODA::BinnedEstimate<int>>(1, 1, 2));
  book(_h_pT_lam, 2, 1, 1);
  book(_h_pT_bar, "TMP/bar_pT", refData(2, 1, 2));
  book(_h_y_lam, 3, 1, 1);
  book(_h_y_bar, "TMP/bar_y", refData(3, 1, 2));
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_c_lam[ix], "TMP/c_lam_" + toString(ix + 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(Cuts::abspid == 5122)) {
    // stuff for the branching ratio
    const double sign = p.pid() / p.abspid();
    if (p.children().size() == 2
        && ((p.children()[0].pid() == sign * 3122 && p.children()[1].pid() == 443)
            || (p.children()[1].pid() == sign * 3122 && p.children()[0].pid() == 443))) {
      _c_lam[0]->fill(1.);
    }
    _c_lam[1]->fill(1.);
    const double pT = p.perp();
    const double y = p.absrap();
    if (y > 2. || pT < 10.) continue;
    if (p.pid() > 0) {
      _h_lam->fill(round(sqrtS()));
      _h_pT_lam->fill(pT);
      _h_y_lam->fill(y);
    }
    else {
      _h_bar->fill(round(sqrtS()));
      _h_pT_bar->fill(pT);
      _h_y_bar->fill(y);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  double fact = crossSection() / nanobarn / sumOfWeights();
  // total cross sectiohn and ratio
  scale(_h_lam, fact);
  scale(_h_bar, fact);
  BinnedEstimatePtr<int> tmpI;
  book(tmpI, 1, 1, 2);
  divide(_h_bar, _h_lam, tmpI);
  // d sig / dpT
  fact *= 1000.;
  scale(_h_pT_lam, fact);
  scale(_h_pT_bar, fact);
  Estimate1DPtr tmp;
  book(tmp, 2, 1, 2);
  divide(_h_pT_bar, _h_pT_lam, tmp);
  // d sig / dy
  scale(_h_y_lam, fact);
  scale(_h_y_bar, fact);
  book(tmp, 3, 1, 2);
  divide(_h_y_bar, _h_y_lam, tmp);
  // now branching ratio for cross sections
  if (_c_lam[1]->effNumEntries() > 0.) {
    scale(_h_lam, *_c_lam[0] / *_c_lam[1]);
    scale(_h_pT_lam, *_c_lam[0] / *_c_lam[1]);
    scale(_h_y_lam, *_c_lam[0] / *_c_lam[1]);
  }
}

/// @}


/// @name Histograms
/// @{
BinnedHistoPtr<int> _h_lam, _h_bar;
Histo1DPtr _h_pT_lam, _h_pT_bar;
Histo1DPtr _h_y_lam, _h_y_bar;
CounterPtr _c_lam[2];
/// @}

};

RIVET_DECLARE_PLUGIN(CMS_2012_I1113442);

} ```