Rivet analyses

title: BABAR_2021_I1844422

Cross sections for $e^+e^-\to 2\pi^+2\pi^-3\pi^0$ and $2\pi^+2\pi^-2\pi^0\eta$ from threshold to 4.5 GeV

Experiment: BABAR (PEP-II)

Inspire ID: 1844422

Status: VALIDATED

Authors: - Peter Richardson

References: - arXiv: 2102.01314

Beams: e+ e-

Beam energies: ANY

Run details: - e+e- to hadrons

Measurement of the cross sections for $e^+e^-\to 2\pi^+2\pi^-3\pi^0$ and $2\pi^+2\pi^-2\pi^0\eta$ from threshold to 4.5 GeV by BaBar. The $2\pi^+2\pi^-\eta$, $\omega\pi^0\eta$, $\pi^+\pi^-2\pi^0\omega$, $\pi^+\pi^-2\pi^0\eta$ resonant subprocesses are also measured.

Source code:BABAR_2021_I1844422.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+e- > 2pi+ 2pi- 3pi0 and 2pi+ 2pi- 2pi0 eta class BABAR_2021_I1844422 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2021_I1844422);


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

/// Book histograms and initialise projections before the run
void init() {

  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  book(_c_2pip2pim3pi0, "TMP/2pip2pim3pi0");
  book(_c_2pip2pimeta, "TMP/2pip2pimeta");
  book(_c_omegapi0eta, "TMP/omegapi0eta");
  book(_c_pippim2pi0omega, "TMP/pippim2pi0omega");
  book(_c_pippim2pi0eta, "TMP/pippim2pi0eta");
  book(_c_2pip2pim2pi0eta, "TMP/2pip2pim2pi0eta");
}

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

/// Perform the per-event analysis
void analyze(const Event& event) {
  const FinalState& fs = apply<FinalState>(event, "FS");
  map<long, int> nCount;
  int ntotal(0);
  for (const Particle& p : fs.particles()) {
    nCount[p.pid()] += 1;
    ++ntotal;
  }
  if (ntotal == 7 && nCount[211] == 2 && nCount[-211] == 2 && nCount[111] == 3) _c_2pip2pim3pi0->fill();
  // intermediate omega and eta mesons
  Particles unstable = apply<FinalState>(event, "UFS").particles(Cuts::pid == 223 or Cuts::pid == 221);
  for (const Particle& p : unstable) {
    if (p.children().empty()) continue;
    map<long, int> nRes = nCount;
    int ncount = ntotal;
    findChildren(p, nRes, ncount);
    // eta
    if (p.pid() == 221) {
      if (ncount == 4) {
        // 2pi+2pi- eta
        if (nRes[211] == 2 && nRes[-211] == 2) {
          _c_2pip2pimeta->fill();
        }
        // pi+pi- 2pi0 eta
        else if (nRes[211] == 1 && nRes[-211] == 1 && nRes[111] == 2) {
          _c_pippim2pi0eta->fill();
        }
      }
      else if (ncount == 6) {
        // 2pi+ 2pi- 2pi0 eta
        if (nRes[211] == 2 && nRes[-211] == 2 && nRes[111] == 2) {
          _c_2pip2pim2pi0eta->fill();
        }
      }
    }
    // omega
    else if (p.pid() == 223) {
      // pi+pi- 2pi0 omega
      if (ncount == 4 && nRes[211] == 1 && nRes[-211] == 1 && nRes[111] == 2) {
        _c_pippim2pi0omega->fill();
      }
    }
    // mode with both eta and omega
    // pi0 omega eta
    for (const Particle& p2 : unstable) {
      if (p2.pid() == p.pid()) continue;
      map<long, int> nResB = nRes;
      int ncountB = ncount;
      findChildren(p2, nResB, ncountB);
      if (ncountB != 1) continue;
      bool matched = true;
      for (const auto& val : nResB) {
        if (abs(val.first) == 111) {
          if (val.second != 1) {
            matched = false;
            break;
          }
        }
        else if (val.second != 0) {
          matched = false;
          break;
        }
      }
      if (matched) {
        _c_omegapi0eta->fill();
        break;
      }
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  for (unsigned int ix = 1; ix < 7; ++ix) {
    double sigma = 0., error = 0.;
    if (ix == 1) {
      sigma = _c_2pip2pim3pi0->val();
      error = _c_2pip2pim3pi0->err();
    }
    else if (ix == 2) {
      sigma = _c_2pip2pimeta->val();
      error = _c_2pip2pimeta->err();
    }
    else if (ix == 3) {
      sigma = _c_omegapi0eta->val();
      error = _c_omegapi0eta->err();
    }
    else if (ix == 4) {
      sigma = _c_pippim2pi0omega->val();
      error = _c_pippim2pi0omega->err();
    }
    else if (ix == 5) {
      sigma = _c_pippim2pi0eta->val();
      error = _c_pippim2pi0eta->err();
    }
    else if (ix == 6) {
      sigma = _c_2pip2pim2pi0eta->val();
      error = _c_2pip2pim2pi0eta->err();
    }
    sigma *= crossSection() / sumOfWeights() / nanobarn;
    error *= crossSection() / sumOfWeights() / nanobarn;
    Estimate1DPtr mult;
    book(mult, ix, 1, 1);
    for (auto& b : mult->bins()) {
      if (inRange(sqrtS() / GeV, b.xMin(), b.xMax())) {
        b.set(sigma, error);
      }
    }
  }
}

///@}


/// @name Histograms
///@{
CounterPtr _c_2pip2pim3pi0, _c_2pip2pimeta, _c_omegapi0eta, _c_pippim2pi0omega, _c_pippim2pi0eta,
    _c_2pip2pim2pi0eta;
///@}

};

RIVET_DECLARE_PLUGIN(BABAR_2021_I1844422);

} ```