Rivet analyses

title: BELLE_2023_I2663731

mass and angular distributions in $B^0\to p(\bar\Lambda^0,\bar\Sigma^0)\pi^-$ decays

Experiment: BELLE (KEKB)

Inspire ID: 2663731

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - arXiv: 2305.18821

Beams: * *

Beam energies: ANY

Run details: - Any process producing B0, originally Upsilon(4S) decays

Measurement of the differential branching ratio with respect to the baryon pair invariant mass for $B^0\to p(\bar\Lambda^0,\bar\Sigma^0)\pi^-$. The differential branching ratio with respect to the proton helicity angle is also measured in the threshold region, i.e. for the baryon pair mass <2.8 GeV. The data were read from the tables in the paper.

Source code:BELLE_2023_I2663731.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/DecayedParticles.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief B0 -> lambdabar/Sigmabar0 p pi- class BELLE_2023_I2663731 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2023_I2663731);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  UnstableParticles ufs = UnstableParticles(Cuts::pid == 511);
  declare(ufs, "UFS");
  DecayedParticles B0(ufs);
  B0.addStable(3122);
  B0.addStable(-3122);
  B0.addStable(3212);
  B0.addStable(-3212);
  declare(B0, "B0");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_h_m[ix], 1, 1, 1 + ix);
    book(_h_theta[ix], 2, 1, 1 + ix);
  }
  book(_cB, "/TMP/nB");
}


/// Perform the per-event analysis
void analyze(const Event& event) {
  DecayedParticles B0 = apply<DecayedParticles>(event, "B0");
  // loop over particles
  for (unsigned int ix = 0; ix < B0.decaying().size(); ++ix) {
    _cB->fill();
    unsigned int imode = 0;
    if (B0.modeMatches(ix, 3, mode1))
      imode = 0;
    else if (B0.modeMatches(ix, 3, mode2))
      imode = 1;
    else
      continue;
    const Particle& pp = B0.decayProducts()[ix].at(2212)[0];
    const Particle& ppim = B0.decayProducts()[ix].at(-211)[0];
    const Particle& LamBar = B0.decayProducts()[ix].at(imode == 0 ? -3122 : -3212)[0];
    double mBB = (pp.mom() + LamBar.mom()).mass();
    _h_m[imode]->fill(mBB);
    if (mBB > 2.8) continue;
    // boost to B rest frame
    LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(
        B0.decaying()[ix].mom().betaVec());
    FourMomentum pLam = boost.transform(LamBar.mom());
    FourMomentum pProton = boost.transform(pp.mom());
    Vector3 axis1 = boost.transform(ppim.mom()).p3().unit();
    LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta((pLam + pProton).betaVec());
    Vector3 axis2 = boost2.transform(pProton).p3().unit();
    _h_theta[imode]->fill(axis1.dot(axis2));
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  scale(_h_m, 1.e6 / *_cB);
  scale(_h_theta, 1.e6 / *_cB);
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _h_m[2], _h_theta[2];
CounterPtr _cB;
const map<PdgId, unsigned int> mode1 = {{2212, 1}, {-3122, 1}, {-211, 1}};
const map<PdgId, unsigned int> mode2 = {{2212, 1}, {-3212, 1}, {-211, 1}};
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2023_I2663731);

} ```