Rivet analyses

title: BELLE_2021_I1748231

$B\to K\ell^+\ell^-$ decays

Experiment: BELLE (KEKB)

Inspire ID: 1748231

Status: VALIDATED NOHEPDATA SINGLEWEIGHT

Authors: - Peter Richardson

References: - JHEP 03 (2021) 105

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0 and B+, original Upsilon(4S) decays

Measurement of the flavour separated differential branching ratio and asymmetries in $B\to K\ell^+\ell^-$ decays.

Source code:BELLE_2021_I1748231.cc

```c++ // -- C++ --

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B -> K l+ l- class BELLE_2021_I1748231 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2021_I1748231);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::abspid == 511 or Cuts::abspid == 521);
  declare(ufs, "UFS");
  DecayedParticles BB(ufs);
  BB.addStable(443);
  BB.addStable(100443);
  BB.addStable(PID::K0S);
  declare(BB, "BB");
  for (unsigned int ix = 0; ix < 4; ++ix)
    for (unsigned int iy = 0; iy < 3; ++iy) {
      book(_h_br[ix][iy], 1, 1 + ix, 1 + iy);
      book(_h_brB[ix][iy], "TMP/h_br_" + toString(ix) + "_" + toString(iy), refData(1, 1 + ix, 1 + iy));
    }
  for (unsigned int ix = 0; ix < 2; ++ix) book(_c[ix], "TMP/nB_" + toString(ix + 1));
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  static const map<PdgId, unsigned int>& mode1 = {{321, 1}, {13, 1}, {-13, 1}};
  static const map<PdgId, unsigned int>& mode1CC = {{-321, 1}, {13, 1}, {-13, 1}};
  static const map<PdgId, unsigned int>& mode2 = {{310, 1}, {13, 1}, {-13, 1}};
  static const map<PdgId, unsigned int>& mode3 = {{321, 1}, {11, 1}, {-11, 1}};
  static const map<PdgId, unsigned int>& mode3CC = {{-321, 1}, {11, 1}, {-11, 1}};
  static const map<PdgId, unsigned int>& mode4 = {{310, 1}, {11, 1}, {-11, 1}};
  DecayedParticles BB = apply<DecayedParticles>(event, "BB");
  // loop over particles
  for (unsigned int ix = 0; ix < BB.decaying().size(); ++ix) {
    if (BB.decaying()[ix].abspid() == 521)
      _c[0]->fill();
    else
      _c[1]->fill();
    int imode = 0;
    if ((BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode1))
        || (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode1CC)))
      imode = 0;
    else if (BB.modeMatches(ix, 3, mode2))
      imode = 1;
    else if ((BB.decaying()[ix].pid() > 0 && BB.modeMatches(ix, 3, mode3))
             || (BB.decaying()[ix].pid() < 0 && BB.modeMatches(ix, 3, mode3CC)))
      imode = 2;
    else if (BB.modeMatches(ix, 3, mode4))
      imode = 3;
    else
      continue;
    int il = imode < 2 ? 13 : 11;
    const Particle& lp = BB.decayProducts()[ix].at(-il)[0];
    const Particle& lm = BB.decayProducts()[ix].at(il)[0];
    double qq = (lp.momentum() + lm.momentum()).mass2();
    for (unsigned int iy = 0; iy < 3; ++iy) {
      _h_br[imode][iy]->fill(qq);
      _h_brB[imode][iy]->fill(qq);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  // ratio of lifetimes
  double rLife = 1.078;
  // normalize BR plots
  for (unsigned int ix = 0; ix < 4; ++ix) {
    for (unsigned int iy = 0; iy < 3; ++iy) {
      if (ix % 2 == 0) {
        scale(_h_br[ix][iy], 1e7 / *_c[0]);
        scale(_h_brB[ix][iy], 1e7 / *_c[0]);
      }
      else {
        scale(_h_br[ix][iy], 1e7 / *_c[1]);
        // KL0 modes 2x needed for isospin stuff
        scale(_h_brB[ix][iy], 2e7 * rLife / *_c[1]);
      }
    }
  }
  // RK and asymmetry plots
  for (unsigned int ix = 0; ix < 3; ++ix) {
    Estimate1DPtr RK;
    book(RK, 3, 1, 1 + ix);
    divide(_h_brB[0][ix], _h_brB[2][ix], RK);
    book(RK, 3, 2, 1 + ix);
    divide(_h_brB[1][ix], _h_brB[3][ix], RK);
    book(RK, 3, 3, 1 + ix);
    for (size_t ibin = 1; ibin < _h_brB[1][ix]->numBins() + 1; ++ibin) {
      double num = _h_brB[0][ix]->bin(ibin).sumW() + _h_brB[1][ix]->bin(ibin).sumW();
      double numErr2 = _h_brB[0][ix]->bin(ibin).sumW2() + _h_brB[1][ix]->bin(ibin).sumW2();
      double den = _h_brB[2][ix]->bin(ibin).sumW() + _h_brB[3][ix]->bin(ibin).sumW();
      double denErr2 = _h_brB[2][ix]->bin(ibin).sumW2() + _h_brB[3][ix]->bin(ibin).sumW2();
      double val(0.), err(0.);
      if (num > 0. && den > 0.) {
        val = num / den;
        err = val * (numErr2 / sqr(num) + denErr2 / sqr(den));
      }
      RK->bin(ibin).set(val, err);
    }
    book(RK, 2, 1, 1 + ix);
    asymm(_h_brB[1][ix], _h_brB[0][ix], RK);
    book(RK, 2, 2, 1 + ix);
    asymm(_h_brB[3][ix], _h_brB[2][ix], RK);
    // average plot
    book(RK, 2, 3, 1 + ix);
    for (unsigned int ibin = 1; ibin < _h_brB[1][ix]->numBins() + 1; ++ibin) {
      double term0 = _h_brB[1][ix]->bin(ibin).sumW() + _h_brB[3][ix]->bin(ibin).sumW();
      double term0Err2 = _h_brB[1][ix]->bin(ibin).sumW2() + _h_brB[3][ix]->bin(ibin).sumW2();
      double term1 = _h_brB[0][ix]->bin(ibin).sumW() + _h_brB[2][ix]->bin(ibin).sumW();
      double term1Err2 = _h_brB[0][ix]->bin(ibin).sumW2() + _h_brB[2][ix]->bin(ibin).sumW2();
      double val(0.), err(0.);
      if (term0 > 0. && term1 > 0.) {
        val = (term0 - term1) / (term0 + term1);
        err = 4. * (sqr(term1) * term0Err2 + sqr(term0) * term1Err2) / pow(term0 + term1, 4);
      }
      RK->bin(ibin).set(val, err);
    }
  }
}

/// @}


/// @name Histograms
/// @{
CounterPtr _c[2];
Histo1DPtr _h_br[4][3], _h_brB[4][3];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2021_I1748231);

} ```