Rivet analyses referenceARGUS_1994_I376001Helicity angles in $B\to J/\psi K^{*}$Experiment: ARGUS (DORIS) Inspire ID: 376001 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Measurement of the $K^*$ and $J/\psi$ helicity angles in the charmonium decay for $B\to J/\psi K^{*}$. The data were read from Figure 2 in the paper which are background subtracted and corrected for efficiency/acceptance. Source code: ARGUS_1994_I376001.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief B -> J/psi K*
9 class ARGUS_1994_I376001 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(ARGUS_1994_I376001);
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==511 || Cuts::abspid==521);
23 declare(ufs, "UFS");
24 // histograms
25 for (unsigned int iz=0; iz<2; ++iz) {
26 book(_h[iz],1,1,1+iz);
27 }
28 }
29
30 bool isKstar(int pid) const {
31 return pid==313 || pid==323;
32 }
33
34 bool isK(int pid) const {
35 return pid==130 || pid==310 || pid==311 || pid==321;
36 }
37
38 bool isPi(int pid) const {
39 return pid==211 || pid==111;
40 }
41
42 /// Perform the per-event analysis
43 void analyze(const Event& event) {
44 UnstableParticles ufs = apply<UnstableParticles>(event, "UFS");
45 for (const Particle & B : ufs.particles()) {
46 if (B.children().size()!=2) continue;
47 Particle jPsi,Kstar;
48 if (B.children()[0].pid()==443 && isKstar(B.children()[1].abspid())) {
49 jPsi = B.children()[0];
50 Kstar = B.children()[1];
51 }
52 else if (B.children()[1].pid()==443 && isKstar(B.children()[0].abspid())) {
53 jPsi = B.children()[1];
54 Kstar = B.children()[0];
55 }
56 else {
57 continue;
58 }
59 if (jPsi.children().size()!=2) continue;
60 // find Kstar decay products
61 Particle K;
62 if (isK (Kstar.children()[0].abspid()) && isPi(Kstar.children()[1].abspid())) {
63 K = Kstar.children()[0];
64 }
65 else if (isK (Kstar.children()[1].abspid()) && isPi(Kstar.children()[0].abspid())) {
66 K = Kstar.children()[1];
67 }
68 else {
69 continue;
70 }
71 // find jPsi decay products
72 Particle oDec;
73 if (jPsi.children()[0].pid()==-13 && jPsi.children()[1].pid()== 13) {
74 oDec = jPsi.children()[1];
75 }
76 else if (jPsi.children()[1].pid()==-13 && jPsi.children()[0].pid()== 13) {
77 oDec = jPsi.children()[0];
78 }
79 else if (jPsi.children()[0].pid()==-11 && jPsi.children()[1].pid()== 11) {
80 oDec = jPsi.children()[1];
81 }
82 else if (jPsi.children()[1].pid()==-11 && jPsi.children()[0].pid()== 11) {
83 oDec = jPsi.children()[0];
84 }
85 else {
86 continue;
87 }
88 // boost to B rest frame
89 LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(B.mom().betaVec());
90 FourMomentum pJPsi = boost.transform(jPsi.mom());
91 FourMomentum pKstar = boost.transform(Kstar.mom());
92 FourMomentum pK = boost.transform(K .mom());
93 FourMomentum pOdec = boost.transform(oDec .mom());
94 // axes
95 Vector3 axisX = pJPsi.p3().unit();
96 Vector3 axisY = (pK.p3()-axisX.dot(pK.p3())*axisX).unit();
97 Vector3 axisZ = axisX.cross(axisY).unit();
98 // kaon helicity angle
99 LorentzTransform boostK = LorentzTransform::mkFrameTransformFromBeta(pKstar.betaVec());
100 double cosK = -axisX.dot(boostK.transform(pK).p3().unit());
101 // transversality angles
102 LorentzTransform boostL = LorentzTransform::mkFrameTransformFromBeta(pJPsi.betaVec());
103 Vector3 axisL = boostL.transform(pOdec).p3().unit();
104 double cosL = axisL.dot(axisZ);
105 // fill hists
106 _h[0]->fill(cosL);
107 _h[1]->fill(cosK);
108 }
109 }
110
111
112 /// Normalise histograms etc., after the run
113 void finalize() {
114 normalize(_h, 1.0, false);
115 }
116
117 /// @}
118
119
120 /// @name Histograms
121 /// @{
122 Histo1DPtr _h[2];
123 /// @}
124
125
126 };
127
128
129 RIVET_DECLARE_PLUGIN(ARGUS_1994_I376001);
130
131}
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