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BABAR_2007_I729388

Cross section for $e^+e^-\to \psi(2S)\pi^+\pi^-$ at energies between 4 and 8 GeV
Experiment: BABAR (PEP-II)
Inspire ID: 729388
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev.Lett. 98 (2007) 212001
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 and 8 GeV using radiative return by BABAR.

Source code: BABAR_2007_I729388.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 BABAR_2007_I729388 : public Analysis {
 11  public:
 12
 13    /// Constructor
 14    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2007_I729388);
 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      Estimate1DPtr  mult;
 86      book(mult, 1, 1, 1);
 87      for (auto& b : mult->bins()) {
 88        if (inRange(sqrtS()/GeV, b.xMin(), b.xMax())) {
 89          b.set(sigma, error);
 90        }
 91      }
 92    }
 93
 94    /// @}
 95
 96
 97    /// @name Histograms
 98    /// @{
 99    CounterPtr _nPsi2s;
100    /// @}
101
102
103  };
104
105
106  RIVET_DECLARE_PLUGIN(BABAR_2007_I729388);
107
108
109}