Rivet analyses

B_c⁺ meson production at 8 TeV

Experiment: LHCB (LHC)

Inspire ID: 1327230

Status: VALIDATED

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 114 (2015) 132001

Beams: p+ p+

Beam energies: (4000.0, 4000.0)GeV

Run details: - hadronic events with B meson

Measurement of the double differential (in p_⟂ and y) ratio B_c⁺/B⁺ meson production at 8 TeV by the LHCb collaboration. The branching ratio for the decay B⁺ → JψK⁺ is taken to be 0.00102 from PDG2023 while by default the branching ratio for B_c⁺ → Jψπ⁺ is measured from the events, however it can be specified using the BCBR option.

Source code:`LHCB_2015_I1327230.cc`

// -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {


  /// @brief B_c production
  class LHCB_2015_I1327230 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2015_I1327230);


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

    /// Book histograms and initialise projections before the run
    void init() {
      declare(UnstableParticles(), "UFS");
      for (unsigned int ib = 0; ib < 2; ++ib) {
        book(_h_pT[ib], "TMP/h_pT_" + toString(ib), refData(2, 1, 1));
        book(_h_y[ib], "TMP/h_y_" + toString(ib), refData(3, 1, 1));
        book(_h_B[ib], {2.0, 2.9, 3.3, 4.5});
        for (unsigned int iy = 0; iy < 3; ++iy) {
          book(_h_B[ib]->bin(iy + 1), "TMP/hB_" + toString(ib) + "_" + toString(iy), refData(1, 1, 1 + iy));
        }
        book(_c_Bc[ib], "TMP/c_Bc_" + toString(ib));
      }
      _brBp = getOption<double>("BPBR", 1.02e-3);
      _brBc = getOption<double>("BCBR", -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::pid == 521 or Cuts::pid == 541)) {
        if (p.pid() == 541) {
          if (p.children().size() == 2
              && ((p.children()[0].pid() == 211 && p.children()[1].pid() == 443)
                  || (p.children()[1].pid() == 211 && p.children()[0].pid() == 443)))
            _c_Bc[0]->fill(1.);
          _c_Bc[1]->fill(1.);
        }
        double absrap = p.absrap();
        if (absrap < 2. || absrap > 4.5) continue;
        double pT = p.perp();
        // select B0
        if (p.pid() == 521) {
          _h_B[1]->fill(absrap, pT);
          _h_pT[1]->fill(pT);
          if (pT < 20.) _h_y[1]->fill(absrap);
        }
        // select B_c+
        else {
          _h_B[0]->fill(absrap, pT);
          _h_pT[0]->fill(pT);
          if (pT < 20.) _h_y[0]->fill(absrap);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      // branching ratio Bc -> J/psi pi+
      if (_brBc < 0.) {
        Estimate0DPtr tmp2;
        book(tmp2, "TMP/br");
        divide(_c_Bc[0], _c_Bc[1], tmp2);
        _brBc = tmp2->val();
      }
      // scale by B+ br (for B_c directly selected before filling histos)
      scale(_h_B[0], _brBc);
      scale(_h_B[1], _brBp);
      for (unsigned int ix = 0; ix < 2; ++ix) divByGroupWidth(_h_B[ix]);
      scale(_h_pT[0], _brBc);
      scale(_h_pT[1], _brBp);
      scale(_h_y[0], _brBc);
      scale(_h_y[1], _brBp);
      for (unsigned int iy = 0; iy < 3; ++iy) {
        Estimate1DPtr tmp;
        book(tmp, 1, 1, 1 + iy);
        divide(_h_B[0]->bin(iy + 1), _h_B[1]->bin(iy + 1), tmp);
        // convert ratio to %
        tmp->scale(100.);
      }
      Estimate1DPtr tmp;
      book(tmp, 2, 1, 1);
      divide(_h_pT[0], _h_pT[1], tmp);
      // convert ratio to %
      tmp->scale(100.);
      book(tmp, 3, 1, 1);
      divide(_h_y[0], _h_y[1], tmp);
      // convert ratio to %
      tmp->scale(100.);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DGroupPtr _h_B[2];
    Histo1DPtr _h_pT[2], _h_y[2];
    CounterPtr _c_Bc[2];
    double _brBp, _brBc;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(LHCB_2015_I1327230);

}

Rivet analyses

Bc+ meson production at 8 TeV

Source code:LHCB_2015_I1327230.cc

B_c⁺ meson production at 8 TeV

Source code:`LHCB_2015_I1327230.cc`