Rivet analyses

title: BELLE_2016_I1444981

Cross section for $\gamma\gamma\to p\bar{p} K^+K^-$

Experiment: BELLE (KEKB)

Inspire ID: 1444981

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev.D 93 (2016) 11, 112017

Beams: 22 22

Beam energies: ANY

Run details: - gamma gamma -> hadrons

Measurement of the cross section for $\gamma\gamma\to p\bar{p} K^+K^-$, including the resonant $\Lambda(1520)^0\bar{p}K^+$ component.

Source code:BELLE_2016_I1444981.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief gamma gamma -> p K+ pbar K- class BELLE_2016_I1444981 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2016_I1444981);


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

/// Book histograms and initialise projections before the run
void init() {
  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(Cuts::abspid == 102134), "UFS");
  // counters
  for (unsigned int ix = 0; ix < 2; ++ix) {
    book(_sigma[ix], "TMP/sigma_" + 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");
  // find the final-state particles
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  // p pbar K+ K-
  if (ntotal == 4 && nCount[2212] == 1 && nCount[-2212] == 1 && nCount[321] == 1 && nCount[-321] == 1)
    _sigma[0]->fill(sqrtS());
  // intermediate Lambda(1520)
  for (const Particle& lam : apply<UnstableParticles>(event, "UFS").particles()) {
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(lam, nRes, ncount);
    int sign = lam.pid() / lam.abspid();
    if (ncount != 2) continue;
    bool matched = true;
    for (const auto& val : nRes) {
      if (val.first == -sign * 2212 || val.first == -sign * 321) {
        if (val.second != 0) {
          matched = false;
          break;
        }
      }
      else if (val.second != 0) {
        matched = false;
        break;
      }
    }
    if (matched) {
      _sigma[1]->fill(sqrtS());
      break;
    }
  }
}


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

/// @}


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

};

RIVET_DECLARE_PLUGIN(BELLE_2016_I1444981);

} ```