Rivet analyses

Mass and helicity angles in B+ → K+K−π+

Experiment: BELLE (KEKB)

Inspire ID: 2099998

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 107 (2023) 3, 032013

Beams: * *

Beam energies: ANY

Run details: - Any process producing B+ mesons, originally Upsilon(4S) decays

Mass and helicity angles in B+ → K+K−π+. The data for the mass distributions was taken from tables I and IV in the paper, and the corrected data for the helicity angles from figure 4.

Source code:BELLE_2023_I2099998.cc

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

namespace Rivet {


  /// @brief B+ -> K+ K- pi+
  class BELLE_2023_I2099998 : public Analysis {
  public:

    /// Constructor
    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2023_I2099998);


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

    /// Book histograms and initialise projections before the run
    void init() {
      // Initialise and register projections
      UnstableParticles ufs = UnstableParticles(Cuts::abspid == 521);
      declare(ufs, "UFS");
      DecayedParticles BP(ufs);
      BP.addStable(PID::K0S);
      BP.addStable(411);
      BP.addStable(-411);
      BP.addStable(421);
      BP.addStable(-421);
      BP.addStable(10441);
      declare(BP, "BP");
      // histograms
      for (unsigned int ix = 0; ix < 3; ++ix) {
        book(_h[ix], 1 + ix, 1, 1);
      }
      book(_c, "TMP/nB");
    }


    /// Perform the per-event analysis
    void analyze(const Event& event) {
      DecayedParticles BP = apply<DecayedParticles>(event, "BP");
      // loop over particles
      for (unsigned int ix = 0; ix < BP.decaying().size(); ++ix) {
        int sign = BP.decaying()[ix].pid() > 0 ? 1 : -1;
        _c->fill();
        if ((sign > 0 and BP.modeMatches(ix, 3, mode)) || (sign < 0 and BP.modeMatches(ix, 3, modeCC))) {
          //      // momenta
          FourMomentum Kp = BP.decayProducts()[ix].at(321 * sign)[0].mom();
          FourMomentum Km = BP.decayProducts()[ix].at(-321 * sign)[0].mom();
          FourMomentum pip = BP.decayProducts()[ix].at(211 * sign)[0].mom();
          // masses
          double mKpi = (Km + pip).mass();
          double mKK = (Kp + Km).mass();
          _h[0]->fill(mKK);
          _h[1]->fill(mKpi);
          if (mKK > 1.1) continue;
          LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
              BP.decaying()[ix].mom().betaVec());
          FourMomentum pKK = boost.transform(Kp + Km);
          LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pKK.betaVec());
          double cTheta = boost2.transform(boost.transform(Kp)).p3().unit().dot(pKK.p3().unit());
          _h[2]->fill(cTheta);
        }
      }
    }


    /// Normalise histograms etc., after the run
    void finalize() {
      scale(_h, 1e7 / *_c);
      normalize(_h[2], 1.0, false);
    }

    /// @}


    /// @name Histograms
    /// @{
    Histo1DPtr _h[3];
    CounterPtr _c;
    const map<PdgId, unsigned int> mode = {{321, 1}, {-321, 1}, {211, 1}};
    const map<PdgId, unsigned int> modeCC = {{321, 1}, {-321, 1}, {-211, 1}};
    /// @}
  };


  RIVET_DECLARE_PLUGIN(BELLE_2023_I2099998);

}