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## Rivet analyses reference

### BESIII_2019_I1773081

$e^+e^-\to\pi^+\pi^-\pi^0$ cross section between 0.7 GeV to 3.0 GeV
Experiment: BESIII (BEPC)
Inspire ID: 1773081
Status: VALIDATED
Authors:
• Peter Richardson
References:
Beams: e+ e-
Beam energies: ANY
Run details:
Cross section for $e^+e^-\to\pi^+\pi^-\pi^0$ cross section for centre-of-mass energies between 0.7 GeV to 3.0 GeV measured by the BES III experiment using radiative return.
  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 // -*- C++ -*- #include "Rivet/Analysis.hh" #include "Rivet/Projections/FinalState.hh" namespace Rivet { /// @brief e+e- to 3 pi from BES class BESIII_2019_I1773081 : public Analysis { public: /// Constructor DEFAULT_RIVET_ANALYSIS_CTOR(BESIII_2019_I1773081); /// @name Analysis methods //@{ /// Book histograms and initialise projections before the run void init() { // Initialise and register projections declare(FinalState(), "FS"); book(_num3pi, "TMP/num3"); } /// Perform the per-event analysis void analyze(const Event& event) { const FinalState& fs = apply(event, "FS"); map nCount; int ntotal(0); for (const Particle& p : fs.particles()) { nCount[p.pid()] += 1; ++ntotal; } if(ntotal!=3) vetoEvent; if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==1) _num3pi->fill(); } /// Normalise histograms etc., after the run void finalize() { double sigma = _num3pi->val(); double error = _num3pi->err(); sigma *= crossSection()/ sumOfWeights() /nanobarn; error *= crossSection()/ sumOfWeights() /nanobarn; Scatter2D temphisto(refData(1, 1, 1)); Scatter2DPtr mult; book(mult, 1, 1, 1); for (size_t b = 0; b < temphisto.numPoints(); b++) { const double x = temphisto.point(b).x(); pair ex = temphisto.point(b).xErrs(); pair ex2 = ex; if(ex2.first ==0.) ex2. first=0.0001; if(ex2.second==0.) ex2.second=0.0001; if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) { mult->addPoint(x, sigma, ex, make_pair(error,error)); } else { mult->addPoint(x, 0., ex, make_pair(0.,.0)); } } } //@} /// @name Histograms //@{ CounterPtr _num3pi; //@} }; DECLARE_RIVET_PLUGIN(BESIII_2019_I1773081); }