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SND_2020_I1806118

Cross Section for $e^+e^-\to K^+K^-\pi^0$ and $\phi\pi^0$ from threshold to 2.1 GeV
Experiment: SND (VEPP-2000)
Inspire ID: 1806118
Status: VALIDATED
Authors:
  • Peter Richardson
References: Beams: e+ e-
Beam energies: ANY
Run details:
  • e+ e- to hadrons

Cross section for $e^+e^-\to K^+K^-\pi^0$ between threshold and 2.1 GeV. The $\phi\pi^0$ radiative subprocess is also measured.

Source code: SND_2020_I1806118.cc
  1// -*- C++ -*-
  2#include "Rivet/Analysis.hh"
  3#include "Rivet/Projections/FinalState.hh"
  4#include "Rivet/Projections/UnstableParticles.hh"
  5
  6namespace Rivet {
  7
  8
  9  /// @brief Add a short analysis description here
 10  class SND_2020_I1806118 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2020_I1806118);
 15
 16
 17    /// @name Analysis methods
 18    ///@{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22
 23      // Initialise and register projections
 24      declare(FinalState(), "FS");
 25      declare(UnstableParticles(), "UFS");
 26
 27      // Book histograms
 28      book( _nKKPi,"TMP/nKKPi" );
 29      book(_nPhiPi,"TMP/nPhiPi");
 30    }
 31
 32    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 33      for (const Particle &child : p.children()) {
 34	if(child.children().empty()) {
 35	  nRes[child.pid()]-=1;
 36	  --ncount;
 37	}
 38	else
 39	  findChildren(child,nRes,ncount);
 40      }
 41    }
 42
 43    /// Perform the per-event analysis
 44    void analyze(const Event& event) {
 45      const FinalState& fs = apply<FinalState>(event, "FS");
 46
 47      map<long,int> nCount;
 48      int ntotal(0);
 49      for (const Particle& p : fs.particles()) {
 50	nCount[p.pid()] += 1;
 51	++ntotal;
 52      }
 53      // KK pi state
 54      if(ntotal==3 && nCount[321]==1 &&
 55	 nCount[-321]==1 && nCount[111]==1)
 56	_nKKPi->fill();
 57      // phi pi state
 58      const FinalState& ufs = apply<FinalState>(event, "UFS");
 59      for (const Particle& p : ufs.particles(Cuts::pid==333)) {
 60	if(p.children().empty()) continue;
 61	map<long,int> nRes = nCount;
 62	int ncount = ntotal;
 63	findChildren(p,nRes,ncount);
 64	if(ncount!=1) continue;
 65	bool matched = true;
 66	for(auto const & val : nRes) {
 67	  if(val.first==111) {
 68	    if(val.second!=1) {
 69	      matched = false;
 70	      break;
 71	      }
 72	  }
 73	  else if(val.second!=0) {
 74	    matched = false;
 75	    break;
 76	  }
 77	}
 78	if(matched) {
 79	  _nPhiPi->fill();
 80	  break;
 81	}
 82      }
 83    }
 84
 85
 86    /// Normalise histograms etc., after the run
 87    void finalize() {
 88      for(unsigned int ix=1;ix<3;++ix) {
 89	double sigma,error;
 90	if(ix==1) {
 91	  sigma = _nKKPi->val();
 92	  error = _nKKPi->err();
 93	}
 94	else {
 95	  sigma = _nPhiPi->val();
 96	  error = _nPhiPi->err();
 97	}
 98    	sigma *= crossSection()/ sumOfWeights() /nanobarn;
 99    	error *= crossSection()/ sumOfWeights() /nanobarn; 
100	Scatter2D temphisto(refData(ix, 1, 1));
101    	Scatter2DPtr  mult;
102        book(mult, ix, 1, 1);
103	for (size_t b = 0; b < temphisto.numPoints(); b++) {
104	  const double x  = temphisto.point(b).x();
105	  pair<double,double> ex = temphisto.point(b).xErrs();
106	  pair<double,double> ex2 = ex;
107	  if(ex2.first ==0.) ex2. first=0.0001;
108	  if(ex2.second==0.) ex2.second=0.0001;
109	  if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
110	    mult->addPoint(x, sigma, ex, make_pair(error,error));
111	  }
112	  else {
113	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
114	  }
115	}
116      }
117    }
118    ///@}
119
120
121    /// @name Histograms
122    ///@{
123    CounterPtr _nKKPi,_nPhiPi;
124    ///@}
125
126
127  };
128
129
130  RIVET_DECLARE_PLUGIN(SND_2020_I1806118);
131
132}