Rivet analyses

π+π− mass distribution in Bs0 → ψ(2S)π+π− and Bs0 → χc1π+π−

Experiment: LHCB (LHC)

Inspire ID: 2635083

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2302.10629

Beams: * *

Beam energies: ANY

Run details: - Any process producing Bs0, originally pp

The π+π− mass distribution in Bs0 → ψ(2S)π+π− and Bs0 → χc1π+π− are measured. The data was extracted from the figures in the paper. There is no consensus as to the nature of the χc1(3872) cc̄ state and therefore we taken its PDG code to be 9030443, i.e. the first unused code for an undetermined spin one cc̄ state. This can be changed using the PID option if a different code is used by the event generator performing the simulation.

Source code:LHCB_2023_I2635083.cc

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

namespace Rivet {


  /// @brief B_s -> psi(2S)/X(3782) pi+pi-
  class LHCB_2023_I2635083 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2023_I2635083);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // set the PDG code
      _pid = getOption<int>("PID", 9030443);
      // projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid==531);
      declare(ufs, "UFS");
      DecayedParticles BS0(ufs);
      BS0.addStable(100443);
      BS0.addStable(_pid);
      declare(BS0, "BS0");
      // histos
      for (unsigned int ix=0; ix<2; ++ix) {
        book(_h[ix], 1, 1, 1+ix);
      }
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
    static const map<PdgId,unsigned int> mode1 = { { 211,1}, {-211,1}, { 100443,1}};
    static const map<PdgId,unsigned int> mode2 = { { 211,1}, {-211,1}, { _pid  ,1}};
      DecayedParticles BS0 = apply<DecayedParticles>(event, "BS0");
      for (unsigned int ix=0; ix<BS0.decaying().size(); ++ix) {
        unsigned int imode=0;
        if      (BS0.modeMatches(ix,3,mode1)) imode=0;
        else if (BS0.modeMatches(ix,3,mode2)) imode=1;
        else continue;
        const Particle& pip  = BS0.decayProducts()[ix].at( 211)[0];
        const Particle& pim  = BS0.decayProducts()[ix].at(-211)[0];
        const double mpipi = (pip.mom()+pim.mom()).mass();
        _h[imode]->fill(mpipi);
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      normalize(_h, 1.0, false);
    }

    /// @}


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


  };


  RIVET_DECLARE_PLUGIN(LHCB_2023_I2635083);

}