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BABAR_2004_I632399

$\phi$ momentum spectra in $\Upsilon(4S)$ decays
Experiment: BABAR (PEP-II)
Inspire ID: 632399
Status: VALIDATED
Authors:
  • Peter Richardson
No references listed
Beams: * *
Beam energies: ANY
Run details:
  • Any process producing Upsilon(4S) originally e+e-

Measurement of the momentum spectrum of $\phi$ mesons produced in $B$ decays at the $\Upsilon(4S)$ resonance.

Source code: BABAR_2004_I632399.cc
 1// -*- C++ -*-
 2#include "Rivet/Analysis.hh"
 3#include "Rivet/Projections/UnstableParticles.hh"
 4
 5namespace Rivet {
 6
 7
 8  /// @brief phi spectrum at 4S
 9  class BABAR_2004_I632399 : public Analysis {
10  public:
11
12    /// Constructor
13    RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2004_I632399);
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(UnstableParticles(), "UFS");
24
25      // Book histograms
26      book(_b_phi, 1, 1, 1);
27      book(_h_phi, 2, 1, 1);
28      book(_c_4S, "/TMP/N4S");
29    }
30
31    void findDecayProducts(const Particle & p, Particles & phi) {
32      for(const Particle & child : p.children()) {
33	if(child.pid()==333)
34	  phi.push_back(child);
35	else if(!child.children().empty())
36	  findDecayProducts(child,phi);
37      }
38    }
39
40    /// Perform the per-event analysis
41    void analyze(const Event& event) {
42      // Find the Upsilons among the unstables
43      const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
44      Particles upsilons = ufs.particles(Cuts::pid==300553);
45      for (const Particle& ups : upsilons) {
46        LorentzTransform cms_boost;
47        if (ups.p3().mod() > 1*MeV)
48          cms_boost = LorentzTransform::mkFrameTransformFromBeta(ups.momentum().betaVec());
49	Particles phis;
50        findDecayProducts(ups, phis);
51	_c_4S->fill();
52
53	for(const Particle & phi : phis) {
54          FourMomentum p2 = cms_boost.transform(phi.momentum());
55	  _h_phi->fill(p2.p3().mod());
56	  _b_phi->fill(0.5);
57	}
58      }
59    }
60
61
62    /// Normalise histograms etc., after the run
63    void finalize() {
64      if(_c_4S->effNumEntries()!=0) {
65	scale(_h_phi   , 0.5/ *_c_4S);
66	scale(_b_phi   , 50./ *_c_4S );
67      }
68    }
69
70    ///@}
71
72
73    /// @name Histograms
74    ///@{
75    Histo1DPtr _h_phi,_b_phi;
76    CounterPtr _c_4S;
77    ///@}
78
79
80  };
81
82
83  RIVET_DECLARE_PLUGIN(BABAR_2004_I632399);
84
85}