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CLEOIII_2006_I728679

Spectra of $\eta^\prime$ mesons in $\Upsilon(1S)$ decays
Experiment: CLEOIII (CESR)
Inspire ID: 728679
Status: VALIDATED
Authors:
  • Peter Richardson
References:
  • Phys.Rev. D74 (2006) 092006
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing Upslion 1S, original $e^+ e^-$

Measurement of the inclusive production of the $\eta^\prime$ mesons in $\Upsilon(1S)$ decays by the CLEO-II experiment. In principle this measurement is superseeds CLEOII_2002_I601701, however given the data for this analysis were extracted from the plots we retain the older analysis.

Source code: CLEOIII_2006_I728679.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief eta' production in Upsilon(1S) decays
 9  class CLEOIII_2006_I728679 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(CLEOIII_2006_I728679);
14
15
16    /// @name Analysis methods
17    //@{
18
19    /// Book histograms and initialise projections before the run
20    void init() {
21      declare(UnstableParticles(), "UFS");
22
23      book(_hist    , 1, 1, 1);
24      book(_mult,"TMP/mult");
25      book(_weightSum,"TMP/weightSum");
26    }
27
28    /// Recursively walk the decay tree to find decay products of @a p
29    void findDecayProducts(Particle mother, Particles& unstable) {
30      for(const Particle & p: mother.children()) {
31        const int id = abs(p.pid());
32	if ( id == 331 ) {
33	  unstable.push_back(p);
34	}
35	else if(!p.children().empty())
36	  findDecayProducts(p, unstable);
37      }
38    }
39
40    /// Perform the per-event analysis
41    void analyze(const Event& event) {
42      // find the Upsilon(1S) mesons
43      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
44      Particles upsilons = ufs.particles(Cuts::pid==553);
45      if(upsilons.empty()) vetoEvent;
46      // loop over them
47      for (const Particle& ups : upsilons) {
48	_weightSum->fill();
49	Particles unstable;
50	// Find the decay products we want
51	findDecayProducts(ups,unstable);
52	LorentzTransform cms_boost;
53	if (ups.p3().mod() > 0.001)
54	  cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
55	double mass = ups.mass();
56	_mult->fill(unstable.size());
57	// fill the spectrum
58	for( const Particle & p : unstable) {
59	  FourMomentum p2 = cms_boost.transform(p.momentum());
60	  double xp = 2.*p2.E()/mass;
61	  _hist->fill(xp);
62	}
63      }
64    }
65
66
67    /// Normalise histograms etc., after the run
68    void finalize() {
69      // spectrum
70      if (_weightSum->val() > 0.)
71        scale(_hist, 1. / *_weightSum);
72      // BR
73      Scatter2DPtr scatter;
74      book(scatter,2, 1, 1, true);
75      scale(_mult,1./ *_weightSum);
76      scatter->point(0).setY(_mult->val(),_mult->err());
77    }
78
79    //@}
80
81
82    /// @name Histograms
83    //@{
84    Histo1DPtr _hist;
85    CounterPtr _mult;
86    CounterPtr _weightSum;
87    //@}
88
89
90  };
91
92
93  RIVET_DECLARE_PLUGIN(CLEOIII_2006_I728679);
94
95}