Rivet analyses

π+π0 mass distribution in Bc+ → J/ψπ+π0 decays

Experiment: LHCB (LHC)

Inspire ID: 2756705

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - JHEP 04 (2024) 151 - arXiv: 2402.05523

Beams: * *

Beam energies: ANY

Run details: - Any process producing B_c+, originally pp

Mass distributions in Bc+ decays to J/ψπ+π0. The background subtracted data were extracted from figure 5 in the paper.

Source code:LHCB_2024_I2756705.cc

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

namespace Rivet {


  /// @brief B_c -> J/psi pi+pi0
  class LHCB_2024_I2756705 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2024_I2756705);

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

    /// Book histograms and initialise projections before the run
    void init() {
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 541);
      declare(ufs, "UFS");
      DecayedParticles BC(ufs);
      BC.addStable(PID::PI0);
      BC.addStable(PID::JPSI);
      declare(BC, "BC");
      book(_h, 1, 1, 1);
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{443, 1}, {211, 1}, {111, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{443, 1}, {-211, 1}, {111, 1}};
      DecayedParticles BC = apply<DecayedParticles>(event, "BC");
      // loop over particles
      for (unsigned int ix = 0; ix < BC.decaying().size(); ++ix) {
        int sign = BC.decaying()[ix].pid() / BC.decaying()[ix].abspid();
        if ((sign == 1 && BC.modeMatches(ix, 3, mode)) || (sign == -1 && BC.modeMatches(ix, 3, modeCC))) {
          const Particle& pi0 = BC.decayProducts()[ix].at(111)[0];
          const Particle& pip = BC.decayProducts()[ix].at(sign * 211)[0];
          FourMomentum ptotal = pi0.momentum() + pip.momentum();
          _h->fill(ptotal.mass());
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1., false);
    }

    /// @}

    /// @name Histograms
    /// @{
    Histo1DPtr _h;
    /// @}
  };


  RIVET_DECLARE_PLUGIN(LHCB_2024_I2756705);

}