Rivet analyses

title: BELLE_2022_I2173361

$e^+e^-\to\Sigma^0\bar{\Sigma}^0$ and $\Sigma^+\bar{\Sigma}^-$ for $\sqrt{s}=2.379-3$ GeV

Experiment: BELLE (KEKB)

Inspire ID: 2173361

Status: VALIDATED NOHEPDATA SINGLEWEIGHT

Authors: - Peter Richardson

References: - arXiv: 2210.16761

Beams: e- e+

Beam energies: ANY

Run details: - e+ e- to hadrons.

Measurement of the cross section for $e^+e^-\to\Sigma^0\bar{\Sigma}^0$ and $\Sigma^+\bar{\Sigma}^-$ for $\sqrt{s}=2.379-3$ GeV by BELLE using raditive events.

Source code:BELLE_2022_I2173361.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+ e- > Sigma Sigmabar class BELLE_2022_I2173361 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2022_I2173361);


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

/// Book histograms and initialise projections before the run
void init() {
  // projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(Cuts::abspid == 3222 || Cuts::abspid == 3212), "UFS");
  // histos
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_sigma[ix], "TMP/c_" + toString(ix + 1), refData(ix + 1, 1, 1));
  }
}

void findChildren(const Particle& p, map<long, int>& nRes, int& ncount) {
  for (const Particle& child : p.children()) {
    if (child.children().empty()) {
      nRes[child.pid()] -= 1;
      --ncount;
    }
    else {
      findChildren(child, nRes, ncount);
    }
  }
}

/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  // total hadronic and muonic cross sections
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  // find the Sigmas
  const FinalState& ufs = apply<UnstableParticles>(event, "UFS");
  for (unsigned int ix = 0; ix < ufs.particles().size(); ++ix) {
    const Particle& p1 = ufs.particles()[ix];
    bool matched = false;
    // check fs
    bool fs = true;
    for (const Particle& child : p1.children()) {
      if (child.pid() == p1.pid()) {
        fs = false;
        break;
      }
    }
    if (!fs) continue;
    // find the children
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p1, nRes, ncount);
    for (unsigned int iy = ix + 1; iy < ufs.particles().size(); ++iy) {
      const Particle& p2 = ufs.particles()[iy];
      if (p2.pid() != -p1.pid()) continue;
      // check fs
      bool fs = true;
      for (const Particle& child : p2.children()) {
        if (child.pid() == p2.pid()) {
          fs = false;
          break;
        }
      }
      if (!fs) continue;
      map<long, int> nRes2 = nRes;
      int ncount2 = ncount;
      findChildren(p2, nRes2, ncount2);
      if (ncount2 != 0) continue;
      matched = true;
      for (const auto& val : nRes2) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        if (abs(p1.pid()) == 3212)
          _sigma[0]->fill(sqrtS());
        else if (abs(p1.pid()) == 3222)
          _sigma[1]->fill(sqrtS());
        break;
      }
    }
    if (matched) break;
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  const double fact = crossSection() / sumOfWeights() / picobarn;
  for (unsigned int iy = 0; iy < 2; ++iy) {
    scale(_sigma[iy], fact);
    Estimate1DPtr tmp;
    book(tmp, iy + 1, 1, 1);
    barchart(_sigma[iy], tmp);
  }
}

/// @}


/// @name Histograms
/// @{
Histo1DPtr _sigma[2];
/// @}

};

RIVET_DECLARE_PLUGIN(BELLE_2022_I2173361);

} ```