Rivet analyses

title: BABAR_2017_I1621593

$e^+e^-\to \pi^+\pi^-\pi^0\pi^0$ cross section from 0.85 to 4.5 GeV

Experiment: BABAR (PEP-II)

Inspire ID: 1621593

Status: VALIDATED NOHEPDATA

Authors: - Peter Richardson

References: - Phys.Rev. D96 (2017) no.9, 092009

Beams: e+ e-

Beam energies: ANY

Run details: - e+ e- to hadrons

Measurement of the cross section for $e^+e^-\to \pi^+\pi^-\pi^0\pi^0$ between 0.85 to 4.5 GeV using radiative return.

Source code:BABAR_2017_I1621593.cc

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

include "Rivet/Analysis.hh"

include "Rivet/Projections/FinalState.hh"

include "Rivet/Projections/UnstableParticles.hh"

namespace Rivet {

/// @brief e+e- > pi+ pi- 2pi0 (including omega) class BABAR_2017_I1621593 : public Analysis { public:

/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2017_I1621593);


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

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

  // Initialise and register projections
  declare(FinalState(), "FS");
  declare(UnstableParticles(), "UFS");
  for (unsigned int ix = 0; ix < 2; ++ix)
    book(_mult[ix], "TMP/mult_" + toString(ix), refData(1 + ix, 1, 1));
}


/// 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 != 4) vetoEvent;
  if (nCount[-211] == 1 && nCount[211] == 1 && nCount[111] == 2) {
    _mult[0]->fill(sqrtS() / GeV);
    const FinalState& ufs = apply<FinalState>(event, "UFS");
    if (!ufs.particles(Cuts::pid == 223).empty()) {
      _mult[1]->fill(sqrtS() / GeV);
    }
  }
}


/// Normalise histograms etc., after the run
void finalize() {
  double fact = crossSection() / sumOfWeights() / nanobarn;
  for (size_t ix = 0; ix < 2; ++ix) {
    scale(_mult[ix], fact);
    Estimate1DPtr tmp;
    book(tmp, 1 + ix, 1, 1);
    barchart(_mult[ix], tmp);
  }
}

/// @}

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

};

RIVET_DECLARE_PLUGIN(BABAR_2017_I1621593);

} ```