Rivet analyses referenceLHCB_2013_I1243156Helicity angle distributions in excited $D$ meson decaysExperiment: LHCB (LHC) Inspire ID: 1243156 Status: VALIDATED Authors:
Beams: * * Beam energies: ANY Run details:
The decays $D^{**} \to D^{*+}\pi^-\to D^0\pi^+\pi^-$ are used to measure the helicity angle, i.e. the angle between the two pions in the rest frame of the $D^*$. The decays of $D_1(2420)^0$, $D^*_2(2460)^0$, $D(2650)^0$, $D(2760)$, $D(2580)$, $D(2740)$, $D(3000)$ were measured,currently the $D(3000)^0$ is not implemented. The data were read from the plots in the papers and therefore for the $D_1(2420)^0$, $D^*_2(2460)^0$ the error bars are the size of the points in the plots. Source code: LHCB_2013_I1243156.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4
5namespace Rivet {
6
7
8 /// @brief Add a short analysis description here
9 class LHCB_2013_I1243156 : public Analysis {
10 public:
11
12 /// Constructor
13 RIVET_DEFAULT_ANALYSIS_CTOR(LHCB_2013_I1243156);
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 , 8,1,1);
27 book(_h_D2_ctheta , 8,1,2);
28 book(_h_DStar2S_ctheta, 9,1,1);
29 book(_h_D3_ctheta , 9,1,2);
30 book(_h_D2S_ctheta ,10,1,1);
31 book(_h_D21D_ctheta ,10,1,2);
32
33 }
34
35
36 /// Recursively walk the decay tree to find decay products of @a p
37 void findDecayProducts(Particle mother, Particles & dstar, Particles & d0, Particles & pi,unsigned int & ncount) {
38 for(const Particle & p: mother.children()) {
39 if(p.abspid()==413)
40 dstar.push_back(p);
41 else if(p.abspid()==421)
42 d0.push_back(p);
43 else if(p.abspid()==211)
44 pi.push_back(p);
45 ncount +=1;
46 }
47 }
48
49 /// Perform the per-event analysis
50 void analyze(const Event& event) {
51 for(const Particle& p : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==425 || Cuts::abspid==10423 ||
52 Cuts::abspid==100423 || Cuts::abspid==427||
53 Cuts::abspid==100421 || Cuts::abspid==10425||
54 Cuts::abspid==20425)) {
55 // decay products
56 Particles dstar,d0,pi;
57 unsigned int ncount=0;
58 findDecayProducts(p,dstar,d0, pi,ncount);
59 if(ncount!=2 || dstar.size()!=1 || pi.size()!=1 || d0.size()!=0 ) 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(pi[0].momentum()).p3().unit();
64 ncount=0;
65 dstar.clear();
66 d0.clear();
67 pi.clear();
68 findDecayProducts(p2,dstar,d0, pi,ncount);
69 if(ncount!=2 || dstar.size()!=0 || 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()==425)
75 _h_D2_ctheta->fill(cTheta);
76 else if(p.abspid()==10423)
77 _h_D1_ctheta->fill(cTheta);
78 else if(p.abspid()==100423)
79 _h_DStar2S_ctheta->fill(cTheta);
80 else if(p.abspid()==427)
81 _h_D3_ctheta->fill(cTheta);
82 else if(p.abspid()==100421)
83 _h_D2S_ctheta->fill(cTheta);
84 else if(p.abspid()==10425 || p.abspid()==20425)
85 _h_D21D_ctheta->fill(cTheta);
86 }
87 }
88
89 /// Normalise histograms etc., after the run
90 void finalize() {
91 normalize(_h_D1_ctheta);
92 normalize(_h_D2_ctheta);
93 normalize(_h_DStar2S_ctheta);
94 normalize(_h_D3_ctheta );
95 normalize(_h_D2S_ctheta );
96 normalize(_h_D21D_ctheta );
97 }
98
99 //@}
100
101
102 /// @name Histograms
103 //@{
104 Histo1DPtr _h_D1_ctheta,_h_D2_ctheta;
105 Histo1DPtr _h_DStar2S_ctheta,_h_D3_ctheta;
106 Histo1DPtr _h_D2S_ctheta,_h_D21D_ctheta;
107 //@}
108
109
110 };
111
112
113 // The hook for the plugin system
114 RIVET_DECLARE_PLUGIN(LHCB_2013_I1243156);
115
116
117}
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