Rivet analyses

title: LHCB_2016_I1394391

Dalitz plot analysis of $D^0\to K^0_SK^\pm\pi^\mp$

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 $D^0\to K^0_SK^\pm\pi^\mp$. 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++ // -- 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);

} ```