Rivet analyses

Mass distributions in B0 → pΛ̄π− and Bs0 → pΛ̄K−

Experiment: LHCB (LHC)

Inspire ID: 1596893

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.Lett. 119 (2017) 4, 041802

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0 and B_s0 mesons, original pp

Mass distributions in B0 → pΛ̄π− and Bs0 → pΛ̄K−. Data read from plots in paper but background subtracted and corrected for efficiency.

Source code:LHCB_2017_I1596893.cc

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

namespace Rivet {


  /// @brief B0 -> p Lambdabar0 pi- and Bs0 -> p Lambdabar0 K-
  class LHCB_2017_I1596893 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2017_I1596893);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 or Cuts::abspid == 531);
      declare(ufs, "UFS");
      DecayedParticles B0(ufs);
      B0.addStable(3122);
      B0.addStable(-3122);
      declare(B0, "B0");
      // book histograms
      for (unsigned int ix = 0; ix < 2; ++ix)
        for (unsigned int iy = 0; iy < 3; ++iy) book(_h[ix][iy], 1 + ix, 1, 1 + iy);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode1 = {{2212, 1}, {-3122, 1}, {-211, 1}};
      static const map<PdgId, unsigned int>& mode1CC = {{-2212, 1}, {3122, 1}, {211, 1}};
      static const map<PdgId, unsigned int>& mode2 = {{2212, 1}, {-3122, 1}, {-321, 1}};
      static const map<PdgId, unsigned int>& mode2CC = {{-2212, 1}, {3122, 1}, {321, 1}};
      DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
      // loop over particles
      for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
        int sign = 1, imode = 0;
        if (B0.decaying()[ix].abspid() == 511) {
          if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode1)) {
            sign = 1;
          }
          else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, mode1CC)) {
            sign = -1;
          }
          else
            continue;
          imode = 0;
        }
        else {
          if (B0.decaying()[ix].pid() > 0 && B0.modeMatches(ix, 3, mode2)) {
            sign = 1;
          }
          else if (B0.decaying()[ix].pid() < 0 && B0.modeMatches(ix, 3, mode2CC)) {
            sign = -1;
          }
          else
            continue;
          imode = 1;
        }
        const Particle& pp = B0.decayProducts()[ix].at(sign * 2212)[0];
        const Particle& LamBar = B0.decayProducts()[ix].at(-sign * 3122)[0];
        const Particle& pim = B0.decayProducts()[ix].at(-sign * (imode == 0 ? 211 : 321))[0];
        _h[imode][0]->fill((pp.momentum() + LamBar.momentum()).mass());
        _h[imode][1]->fill((pp.momentum() + pim.momentum()).mass());
        _h[imode][2]->fill((pim.momentum() + LamBar.momentum()).mass());
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      for (unsigned int ix = 0; ix < 2; ++ix)
        for (unsigned int iy = 0; iy < 3; ++iy) normalize(_h[ix][iy], 1., false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[2][3];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(LHCB_2017_I1596893);

}