Rivet analyses referenceLHCB_2016_I1414195Helicity angle distributions in excited $D_s$ meson decaysExperiment: LHCB (LHC) Inspire ID: 1414195 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
The decays $D_s^{**} \to D^{*+}K^0_S\to D^0\pi^+K^0_S$ are used to measure the helicity angle, i.e. the angle between the pion and kaon in the rest frame of the $D^*$. The decays of $D_{s1}(2536)^+$, $D^*_{s2}(2573)^+$, $D_{s1}^*(2700)^+$, $D_{sJ}^*(2860)^+$, $D_{sJ}(3040)^+$ were measured, currently the $D_{sJ}(3040)^+$ is not implemented. It is unclear if the $D_{sJ}^*(2860)^+$ is the $D_{s1}^*(2860)^+$, $D_{s3}^*(2860)^+$ or a mixture of the two. This histogram is therefore filled we with each state and the admixture. The data were extracted from the files supplied on the LHCb website. Source code: LHCB_2016_I1414195.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief D**_s decays
9 class LHCB_2016_I1414195 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2016_I1414195);
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(_h_D1_ctheta, 1,1,1);
27 book(_h_D2_ctheta, 1,1,2);
28 book(_h_DStar_ctheta, 2,1,1);
29 book(_h_D3_ctheta[0], 2,1,2);
30 book(_h_D3_ctheta[1], 2,1,4);
31 book(_h_D3_ctheta[2], 2,1,5);
32 }
33
34
35 /// Recursively walk the decay tree to find decay products of @a p
36 void findDecayProducts(Particle mother, Particles & dstar, Particles & d0, Particles & K0, Particles & pi, unsigned int & ncount) {
37 for(const Particle & p: mother.children()) {
38 if(p.abspid()==413)
39 dstar.push_back(p);
40 else if(p.abspid()==421)
41 d0.push_back(p);
42 else if(p.abspid()==130 || p.abspid()==130 || p.abspid()==311)
43 K0.push_back(p);
44 else if(p.abspid()==211)
45 pi.push_back(p);
46 ncount +=1;
47 }
48 }
49
50 /// Perform the per-event analysis
51 void analyze(const Event& event) {
52 for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==435 || Cuts::abspid==10433 ||
53 Cuts::abspid==100433 || Cuts::abspid==437 ||
54 Cuts::abspid==30433)) {
55 // decay products
56 Particles dstar,d0,K0,pi;
57 unsigned int ncount=0;
58 findDecayProducts(p, dstar, d0, K0, pi, ncount);
59 if(ncount!=2 || dstar.size()!=1 || K0.size()!=1 ) continue;
60 if(dstar[0].pid()/p.pid()<0) continue;
61 Particle p2 = dstar[0];
62 LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(p2.momentum().betaVec());
63 Vector3 d1 = boost.transform(K0[0].momentum()).p3().unit();
64 ncount=0;
65 dstar.clear();
66 d0.clear();
67 pi.clear();
68 findDecayProducts(p2, dstar, d0, K0, pi, ncount);
69 if(ncount!=2 || pi.size()!=1 || d0.size()!=1 ) continue;
70 if(pi[0].pid()/p2.pid()<0) continue;
71 Vector3 d2 = boost.transform(pi[0].momentum()).p3().unit();
72 double cTheta = d1.dot(d2);
73 // decay angles
74 if(p.abspid()==435)
75 _h_D2_ctheta->fill(cTheta);
76 else if(p.abspid()==10433)
77 _h_D1_ctheta->fill(cTheta);
78 else if(p.abspid()==100433)
79 _h_DStar_ctheta->fill(cTheta);
80 else if(p.abspid()==30433) {
81 _h_D3_ctheta[0]->fill(cTheta);
82 _h_D3_ctheta[2]->fill(cTheta);
83 }
84 else if(p.abspid()==437) {
85 _h_D3_ctheta[1]->fill(cTheta);
86 _h_D3_ctheta[2]->fill(cTheta);
87 }
88 }
89 }
90
91
92 /// Normalise histograms etc., after the run
93 void finalize() {
94 normalize(_h_D1_ctheta);
95 normalize(_h_D2_ctheta);
96 normalize(_h_DStar_ctheta);
97 normalize(_h_D3_ctheta[0]);
98 normalize(_h_D3_ctheta[1]);
99 normalize(_h_D3_ctheta[2]);
100 }
101
102 ///@}
103
104
105 /// @name Histograms
106 ///@{
107 Histo1DPtr _h_D1_ctheta,_h_D2_ctheta,_h_DStar_ctheta,_h_D3_ctheta[3];
108 ///@}
109
110
111 };
112
113
114 RIVET_DECLARE_PLUGIN(LHCB_2016_I1414195);
115
116}
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