Rivet analyses referenceBABAR_2006_I719581Decay asymmetries in the decay of $\Omega^-$ baryons produced in $\Xi^0_c$ and $\Omega_c^0$ decaysExperiment: BABAR (PEP-II) Inspire ID: 719581 Status: VALIDATED Authors:
Beam energies: ANY Run details:
Measurement of the decay asymmetries in $\Xi^0_c\to\Omega^-K^+$ and $\Omega^-_c\to\Omega^-\pi^+$ by the BaBar experiment. In both cases the decay mode $\Omega^-\to\Lambda^0K^-$ was used. This analysis is useful for testing spin correlations in hadron decays. Source code: BABAR_2006_I719581.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief Omega decay asymmetries
9 class BABAR_2006_I719581 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(BABAR_2006_I719581);
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 // Book histograms
25 book(_h_ctheta_xic ,1,1,1);
26 book(_h_ctheta_omegac,2,1,1);
27 }
28
29
30 /// Perform the per-event analysis
31 void analyze(const Event& event) {
32 // loop over Xi_c0 baryons and Omega_c0 baryons
33 for(const Particle& baryon : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==4132 || Cuts::abspid==4332 )) {
34 int sign = baryon.pid()/baryon.abspid();
35 if(baryon.children().size()!=2) continue;
36 Particle baryon1,meson1;
37 if(baryon.abspid()==4132) {
38 if(baryon.children()[0].pid()==sign*3334 &&
39 baryon.children()[1].pid()==sign*321) {
40 baryon1 = baryon.children()[0];
41 meson1 = baryon.children()[1];
42 }
43 else if(baryon.children()[1].pid()==sign*3332 &&
44 baryon.children()[0].pid()==sign*321) {
45 baryon1 = baryon.children()[1];
46 meson1 = baryon.children()[0];
47 }
48 else
49 continue;
50 }
51 else {
52 if(baryon.children()[0].pid()==sign*3334 &&
53 baryon.children()[1].pid()==sign*211) {
54 baryon1 = baryon.children()[0];
55 meson1 = baryon.children()[1];
56 }
57 else if(baryon.children()[1].pid()==sign*3334 &&
58 baryon.children()[0].pid()==sign*211) {
59 baryon1 = baryon.children()[1];
60 meson1 = baryon.children()[0];
61 }
62 else
63 continue;
64 }
65 Particle baryon2,meson2;
66 if(baryon1.children()[0].pid()== sign*3122 &&
67 baryon1.children()[1].pid()==-sign*321) {
68 baryon2 = baryon1.children()[0];
69 meson2 = baryon1.children()[1];
70 }
71 else if(baryon1.children()[1].pid()== sign*3122 &&
72 baryon1.children()[0].pid()==-sign*321) {
73 baryon2 = baryon1.children()[1];
74 meson2 = baryon1.children()[0];
75 }
76 else
77 continue;
78 // first boost to the Xic/Omegac rest frame
79 LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(baryon.momentum().betaVec());
80 FourMomentum pbaryon1 = boost1.transform(baryon1.momentum());
81 FourMomentum pbaryon2 = boost1.transform(baryon2.momentum());
82 // to omega rest frame
83 LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pbaryon1.betaVec());
84 Vector3 axis = pbaryon1.p3().unit();
85 FourMomentum pp = boost2.transform(pbaryon2);
86 // calculate angle
87 double cTheta = pp.p3().unit().dot(axis);
88 if(baryon.abspid()==4132)
89 _h_ctheta_xic->fill(cTheta,1.);
90 else
91 _h_ctheta_omegac->fill(cTheta,1.);
92 }
93 }
94
95
96 /// Normalise histograms etc., after the run
97 void finalize() {
98
99 normalize(_h_ctheta_xic);
100 normalize(_h_ctheta_omegac);
101 }
102
103 /// @}
104
105
106 /// @name Histograms
107 /// @{
108 Histo1DPtr _h_ctheta_xic,_h_ctheta_omegac;
109 /// @}
110
111
112 };
113
114
115 RIVET_DECLARE_PLUGIN(BABAR_2006_I719581);
116
117
118}
|
