Rivet analyses

Dalitz plot analysis of D0 → KS0K±π∓

Experiment: LHCB (LHC)

Inspire ID: 1394391

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 93 (2016) 5, 052018

Beams: * *

Beam energies: ANY

Run details: none listed

Measurement of Kinematic distributions in the decays D0 → KS0K±π∓. The data were extracted from the plots in the paper. Resolution/acceptance effects have been not unfolded but an efficiency function base on Fig 4 of the paper is applied. Given the agreement with the model in the paper this analysis should only be used for qualitative studies.

Source code:LHCB_2016_I1394391.cc

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

namespace Rivet {


  /// @brief  D0 -> KS) K+/- pi-/+
  class LHCB_2016_I1394391 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2016_I1394391);


    /// @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);
      D0.addStable(PID::ETA);
      D0.addStable(PID::ETAPRIME);
      declare(D0, "D0");
      // histograms
      book(_h_Kmpip, 1, 1, 1);
      book(_h_K0pip, 1, 1, 2);
      book(_h_K0Km, 1, 1, 3);
      book(_h_Kppim, 2, 1, 1);
      book(_h_K0pim, 2, 1, 2);
      book(_h_K0Kp, 2, 1, 3);
      book(_dalitz[0], "dalitz_1", 50, 0.3, 2.0, 50, 0.3, 2.);
      book(_dalitz[1], "dalitz_2", 50, 0.3, 2.0, 50, 0.3, 2.);
    }

    double efficiency(const double& x, const double& y) {
      double X = x - 2., Y = y - 1.;
      static const double E0 = 5.8096, Ex = -3.645, Ey = -3.174, Ex2 = 0.831, Exy = 2.131, Ey2 = 4.43,
                          Ex3 = -0.427, Ex2y = 2.65, Exy2 = 1.50, Ey3 = -3.92;
      return E0 + Ex * X + Ey * Y + Ex2 * sqr(X) + Ey2 * sqr(Y) + Exy * X * Y + Ex3 * pow(X, 3)
          + Ex2y * sqr(X) * Y + Exy2 * X * sqr(Y) + Ey3 * pow(Y, 3);
    }

    /// Perform the per-event analysis
    void analyze(const Event& event) {
      static const map<PdgId, unsigned int>& mode = {{321, 1}, {-211, 1}, {310, 1}};
      static const map<PdgId, unsigned int>& modeCC = {{-321, 1}, {211, 1}, {310, 1}};
      DecayedParticles D0 = apply<DecayedParticles>(event, "D0");
      // loop over particles
      for (unsigned int ix = 0; ix < D0.decaying().size(); ++ix) {
        if (!D0.modeMatches(ix, 3, mode) && !D0.modeMatches(ix, 3, modeCC)) continue;
        const Particles& K0 = D0.decayProducts()[ix].at(310);
        int sign = D0.decaying()[ix].pid() / 421;
        const Particles& pip = D0.decayProducts()[ix].find(sign * 211) == D0.decayProducts()[ix].end()
            ? Particles()
            : D0.decayProducts()[ix].at(sign * 211);
        const Particles& pim = D0.decayProducts()[ix].find(-sign * 211) == D0.decayProducts()[ix].end()
            ? Particles()
            : D0.decayProducts()[ix].at(-sign * 211);
        const Particles& Kp = D0.decayProducts()[ix].find(sign * 321) == D0.decayProducts()[ix].end()
            ? Particles()
            : D0.decayProducts()[ix].at(sign * 321);
        const Particles& Km = D0.decayProducts()[ix].find(-sign * 321) == D0.decayProducts()[ix].end()
            ? Particles()
            : D0.decayProducts()[ix].at(-sign * 321);
        // K0S K- pi+
        if (Km.size() == 1 && pip.size() == 1) {
          double mK0pip = (K0[0].momentum() + pip[0].momentum()).mass2();
          double mKmpip = (Km[0].momentum() + pip[0].momentum()).mass2();
          double mKK = (K0[0].momentum() + Km[0].momentum()).mass2();
          double eff = efficiency(mKK, mK0pip);
          _h_K0Km->fill(mKK, eff);
          _h_K0pip->fill(mK0pip, eff);
          _h_Kmpip->fill(mKmpip, eff);
          _dalitz[0]->fill(mKmpip, mK0pip);
        }
        // K0S K+ pi-
        else if (Kp.size() == 1 && pim.size() == 1) {
          double mK0pim = (K0[0].momentum() + pim[0].momentum()).mass2();
          double mKppim = (Kp[0].momentum() + pim[0].momentum()).mass2();
          double mKK = (K0[0].momentum() + Kp[0].momentum()).mass2();
          double eff = efficiency(mKK, mK0pim);
          _h_K0Kp->fill(mKK, eff);
          _h_K0pim->fill(mK0pim, eff);
          _h_Kppim->fill(mKppim, eff);
          _dalitz[1]->fill(mKppim, mK0pim);
        }
      }
    }


    /// Normalise histograms etc., after the runbook
    void finalize() {
      normalize(_h_Kmpip);
      normalize(_h_K0pip);
      normalize(_h_K0Km);
      normalize(_h_Kppim);
      normalize(_h_K0pim);
      normalize(_h_K0Kp);
      normalize(_dalitz[0]);
      normalize(_dalitz[1]);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h_Kmpip, _h_K0pip, _h_K0Km;
    Histo1DPtr _h_Kppim, _h_K0pim, _h_K0Kp;
    Histo2DPtr _dalitz[2];
    /// @}
  };


  RIVET_DECLARE_PLUGIN(LHCB_2016_I1394391);

}