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BELLE_2007_I756643

Cross section for $e^+e^-\to \psi(2S)\pi^+\pi^-$ at energies between 4.025 and 5.475 GeV
Experiment: BELLE (KEKB)
Inspire ID: 756643
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 99 (2007) 142002, 2007
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to \psi(2S)\pi^+\pi^-$ at energies between 4.025 and 5.475 GeV using radiative return by BELLE.

Source code: BELLE_2007_I756643.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 BELLE_2007_I756643 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I756643);
 15
 16
 17    /// @name Analysis methods
 18    //@{
 19
 20    /// Book histograms and initialise projections before the run
 21    void init() {
 22      declare(FinalState(), "FS");
 23      declare(UnstableParticles(), "UFS");
 24      book(_nPsi2s, "TMP/psi2s");
 25    }
 26
 27    void findChildren(const Particle & p,map<long,int> & nRes, int &ncount) {
 28      for (const Particle &child : p.children()) {
 29	if(child.children().empty()) {
 30	  --nRes[child.pid()];
 31	  --ncount;
 32	}
 33	else
 34	  findChildren(child,nRes,ncount);
 35      }
 36    }
 37
 38    /// Perform the per-event analysis
 39    void analyze(const Event& event) {
 40      const FinalState& fs = apply<FinalState>(event, "FS");
 41      map<long,int> nCount;
 42      int ntotal(0);
 43      for (const Particle& p : fs.particles()) {
 44	nCount[p.pid()] += 1;
 45	++ntotal;
 46      }
 47      const FinalState& ufs = apply<FinalState>(event, "UFS");
 48      for (const Particle& p : ufs.particles()) {
 49	if(p.children().empty()) continue;
 50	// find the psi(2S)
 51	if(p.pid()==100443) {
 52	  map<long,int> nRes = nCount;
 53	  int ncount = ntotal;
 54	  findChildren(p,nRes,ncount);
 55	  // omega pi+pi-
 56	  if(ncount!=2) continue;
 57	  bool matched = true;
 58	  for(auto const & val : nRes) {
 59	    if(abs(val.first)==211) {
 60	      if(val.second !=1) {
 61		matched = false;
 62		break;
 63	      }
 64	    }
 65	    else if(val.second!=0) {
 66	      matched = false;
 67	      break;
 68	    }
 69	  }
 70	  if(matched) {
 71	    _nPsi2s->fill();
 72	    break;
 73	  }
 74	}
 75      }
 76    }
 77
 78
 79    /// Normalise histograms etc., after the run
 80    void finalize() {
 81      double sigma =  _nPsi2s->val();
 82      double error = _nPsi2s->err();
 83      sigma *= crossSection()/ sumOfWeights() /picobarn;
 84      error *= crossSection()/ sumOfWeights() /picobarn; 
 85      Scatter2D temphisto(refData(1, 1, 1));
 86      Scatter2DPtr  mult;
 87      book(mult, 1, 1, 1);
 88      for (size_t b = 0; b < temphisto.numPoints(); b++) {
 89	const double x  = temphisto.point(b).x();
 90	pair<double,double> ex = temphisto.point(b).xErrs();
 91	pair<double,double> ex2 = ex;
 92	if(ex2.first ==0.) ex2. first=0.0001;
 93	if(ex2.second==0.) ex2.second=0.0001;
 94	if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
 95	  mult->addPoint(x, sigma, ex, make_pair(error,error));
 96	}
 97	else {
 98	  mult->addPoint(x, 0., ex, make_pair(0.,.0));
 99	}
100      }
101    }
102
103    //@}
104
105
106    /// @name Histograms
107    //@{
108    CounterPtr _nPsi2s;
109    //@}
110
111
112  };
113
114
115  // The hook for the plugin system
116  RIVET_DECLARE_PLUGIN(BELLE_2007_I756643);
117
118
119}