Rivet analyses referenceBELLE_2013_I1124584Helicity angles in $B_s^0\to D_s^{*+}D_s^{*-}$Experiment: BELLE (KEKB) Inspire ID: 1124584 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Helicity angle distributions in $B^0\to D^{*+}D^{*-}$ decays Source code: BELLE_2013_I1124584.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief Bs0 -> Ds* Ds*
9 class BELLE_2013_I1124584 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2013_I1124584);
14
15
16 /// @name Analysis methods
17 /// @{
18
19 /// Book histograms and initialise projections before the run
20 void init() {
21 // Initialise and register projections
22 UnstableParticles ufs = UnstableParticles(Cuts::abspid==531);
23 declare(ufs, "UFS");
24 // histograms
25 for(unsigned int ix=0;ix<2;++ix)
26 book(_h[ix],1,1,1+ix);
27 }
28
29
30 /// Perform the per-event analysis
31 void analyze(const Event& event) {
32 Particles BS0 = apply<UnstableParticles>(event, "UFS").particles();
33 for(const Particle & p : BS0) {
34 if(p.children().size()!=2) continue;
35 if(p.children()[0].pid()!=-p.children()[1].pid()) continue;
36 if(p.children()[0].abspid()!=433) continue;
37 Particle Dp = p.children()[0];
38 Particle Dm = p.children()[1];
39 if (p.pid()>0 && Dp.pid()<0) swap(Dp,Dm);
40 else if(p.pid()<0 && Dp.pid()>0) swap(Dp,Dm);
41 // boost to rest frame
42 LorentzTransform boostB = LorentzTransform::mkFrameTransformFromBeta(p.momentum().betaVec());
43 FourMomentum pB = boostB.transform(p.momentum());
44 if(Dp.children().size()==2) {
45 Particle gamma;
46 bool found = true;
47 if(Dp.children()[0].pid()==PID::GAMMA &&
48 Dp.children()[1].abspid()==431)
49 gamma = Dp.children()[0];
50 else if (Dp.children()[1].pid()==PID::GAMMA &&
51 Dp.children()[0].abspid()==431)
52 gamma = Dp.children()[1];
53 else
54 found = false;
55 if( found) {
56 FourMomentum pD = boostB.transform(Dp.momentum());
57 FourMomentum pgamma = boostB.transform(gamma.momentum());
58 LorentzTransform boostD = LorentzTransform::mkFrameTransformFromBeta(pD.betaVec());
59 Vector3 axisB = boostD.transform(pB).p3().unit();
60 Vector3 axisG = boostD.transform(pgamma).p3().unit();
61 _h[0]->fill(axisB.dot(axisG));
62 }
63 }
64 if(Dm.children().size()==2) {
65 Particle gamma;
66 bool found = true;
67 if(Dm.children()[0].pid()==PID::GAMMA &&
68 Dm.children()[1].abspid()==431)
69 gamma = Dm.children()[0];
70 else if (Dm.children()[1].pid()==PID::GAMMA &&
71 Dm.children()[0].abspid()==431)
72 gamma = Dm.children()[1];
73 else
74 found = false;
75 if( found) {
76 FourMomentum pD = boostB.transform(Dm.momentum());
77 FourMomentum pgamma = boostB.transform(gamma.momentum());
78 LorentzTransform boostD = LorentzTransform::mkFrameTransformFromBeta(pD.betaVec());
79 Vector3 axisB = boostD.transform(pB).p3().unit();
80 Vector3 axisG = boostD.transform(pgamma).p3().unit();
81 _h[1]->fill(axisB.dot(axisG));
82 }
83 }
84 }
85 }
86
87
88 /// Normalise histograms etc., after the run
89 void finalize() {
90 for(unsigned int ix=0;ix<2;++ix)
91 normalize(_h[ix],1.,false);
92 }
93
94 /// @}
95
96
97 /// @name Histograms
98 /// @{
99 Histo1DPtr _h[2];
100 /// @}
101
102
103 };
104
105
106 RIVET_DECLARE_PLUGIN(BELLE_2013_I1124584);
107
108}
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