Rivet analyses

Mass distributions in the decay D0 → K−π+μ+μ−

Experiment: LHCB (LHC)

Inspire ID: 1401225

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Lett.B 757 (2016) 558-567

Beams: * *

Beam energies: ANY

Run details: - Any process producing D0

Kinematic distributions in the decay D0 → K−π+μ+μ−. Resolution/acceptance effects have been not unfolded.

Source code:LHCB_2015_I1401225.cc

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

namespace Rivet {


  /// @brief
  class LHCB_2015_I1401225 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2015_I1401225);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 421);
      declare(ufs, "UFS");
      DecayedParticles D0(ufs);
      D0.addStable(PID::PI0);
      D0.addStable(PID::K0S);
      declare(D0, "D0");
      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>& mode = {{321, 1}, {211, 1}, {13, 1}, {-13, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{321, 1}, {-211, 1}, {13, 1}, {-13, 1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for (unsigned int ix = 0; ix < D0.decaying().size(); ++ix) {
        int sign = 1;
        if (D0.decaying()[ix].pid() > 0 && D0.modeMatches(ix, 4, mode)) {
          sign = 1;
        }
        else if (D0.decaying()[ix].pid() < 0 && D0.modeMatches(ix, 4, modeCC)) {
          sign = -1;
        }
        else
          continue;
        const Particle& Kp = D0.decayProducts()[ix].at(-sign * 321)[0];
        const Particle& pim = D0.decayProducts()[ix].at(sign * 211)[0];
        const Particle& mup = D0.decayProducts()[ix].at(13)[0];
        const Particle& mum = D0.decayProducts()[ix].at(-13)[0];
        _h[0]->fill((Kp.momentum() + pim.momentum()).mass() / MeV);
        _h[1]->fill((mum.momentum() + mup.momentum()).mass() / MeV);
      }
    }


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

    /// @}


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


  RIVET_DECLARE_PLUGIN(LHCB_2015_I1401225);

}