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SND_2001_I579319

Cross section for $e^+e^-2\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$ between 1 and 1.4 GeV
Experiment: SND (VEPP-2M)
Inspire ID: 579319
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • INP-2001-34 (2001)
Beams: e+ e-
Beam energies: ANY
Run details:
  • e+e- to hadrons

Measurement of the cross section for $e^+e^-\to\pi^+2\pi^-$ and $\pi^+\pi^-2\pi^0$ between 1 and 1.4 GeV

Source code: SND_2001_I579319.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/FinalState.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief Add a short analysis description here
 9  class SND_2001_I579319 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(SND_2001_I579319);
14
15
16    /// @name Analysis methods
17    //@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21
22      // Initialise and register projections
23      declare(FinalState(), "FS");
24
25      // Book histograms
26      book(_npion1, "TMP/pion1");
27      book(_npion2, "TMP/pion2");
28    }
29
30
31    /// Perform the per-event analysis
32    void analyze(const Event& event) {
33      const FinalState& fs = apply<FinalState>(event, "FS");
34
35      map<long,int> nCount;
36      int ntotal(0);
37      for (const Particle& p : fs.particles()) {
38	nCount[p.pid()] += 1;
39	++ntotal;
40      }
41      if(ntotal!=4) vetoEvent;
42      if(nCount[-211]==2&&nCount[211]==2)
43	_npion1->fill();
44      else if(nCount[-211]==1&&nCount[211]==1&&nCount[111]==2)
45	_npion2->fill();
46    }
47
48
49    /// Normalise histograms etc., after the run
50    void finalize() {
51      for(unsigned int ix=1;ix<3;++ix) {
52	double sigma,error;
53	if(ix==1) {
54	  sigma = _npion1->val();
55	  error = _npion1->err();
56	}
57	else {
58	  sigma = _npion2->val();
59	  error = _npion2->err();
60	}
61	sigma *= crossSection()/ sumOfWeights() /nanobarn;
62	error *= crossSection()/ sumOfWeights() /nanobarn; 
63	Scatter2D temphisto(refData(ix, 1, 1));
64	Scatter2DPtr mult;
65	book(mult, ix, 1, 1);
66	for (size_t b = 0; b < temphisto.numPoints(); b++) {
67	  const double x  = temphisto.point(b).x();
68	  pair<double,double> ex = temphisto.point(b).xErrs();
69	  pair<double,double> ex2 = ex;
70	  if(ex2.first ==0.) ex2. first=0.0001;
71	  if(ex2.second==0.) ex2.second=0.0001;
72	  if (inRange(sqrtS()/GeV, x-ex2.first, x+ex2.second)) {
73	    mult->addPoint(x, sigma, ex, make_pair(error,error));
74	  }
75	  else {
76	    mult->addPoint(x, 0., ex, make_pair(0.,.0));
77	  }
78	}
79      }	
80    }
81
82    //@}
83
84
85    /// @name Histograms
86    //@{
87    CounterPtr _npion1,_npion2;
88    //@}
89
90
91  };
92
93
94  // The hook for the plugin system
95  RIVET_DECLARE_PLUGIN(SND_2001_I579319);
96
97
98}