Rivet analyses referenceBELLE_2007_I748975$B^+\to p \bar{\Lambda}^0\gamma$, $B^+\to p \bar{\Lambda}^0\pi^0$ and $B^0\to p \bar{\Lambda}^0\pi^-$Experiment: BELLE (KEKB) Inspire ID: 748975 Status: VALIDATED NOHEPDATA Authors:
Beam energies: ANY Run details:
Mass and angular distributions in $B^+\to p \bar{\Lambda}^0\gamma$, $B^+\to p \bar{\Lambda}^0\pi^0$ and $B^0\to p \bar{\Lambda}^0\pi^-$ decays. The mass distributions, $\alpha$ parameters and average $\bar{\Lambda}^0$ energies were read from the table in the paper, while the $\cos\theta_p$ distributions were extracted from the figures. Source code: BELLE_2007_I748975.cc 1// -*- C++ -*-
2#include "Rivet/Analysis.hh"
3#include "Rivet/Projections/UnstableParticles.hh"
4#include "Rivet/Projections/DecayedParticles.hh"
5
6namespace Rivet {
7
8
9 /// @brief B-> p Lambdabar X decays
10 class BELLE_2007_I748975 : public Analysis {
11 public:
12
13 /// Constructor
14 RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2007_I748975);
15
16
17 /// @name Analysis methods
18 /// @{
19
20 /// Book histograms and initialise projections before the run
21 void init() {
22 UnstableParticles ufs = UnstableParticles(Cuts::abspid==511 || Cuts::abspid==521);
23 declare(ufs, "UFS");
24 DecayedParticles BB(ufs);
25 BB.addStable(PID::PI0);
26 BB.addStable( 3122);
27 BB.addStable(-3122);
28 declare(BB, "BB");
29 // histos
30 for (unsigned int iy=0; iy<3; ++iy) {
31 book(_h_mass [iy],1,1,1+iy);
32 book(_h_cosp [iy],2,1,1+iy);
33 book(_h_alpha[iy][0],3,1,1+iy);
34 book(_h_alpha[iy][1],"TMP/h_alpha_"+toString(1+iy));
35 book(_h_E [iy][0],4,1,1+iy);
36 book(_h_E [iy][1],"TMP/h_E_"+toString(1+iy));
37 }
38 for (unsigned int iy=0;iy<2;++iy) {
39 book(_c[iy],"TMP/c_"+toString(iy+1));
40 }
41 }
42
43
44 /// Perform the per-event analysis
45 void analyze(const Event& event) {
46 DecayedParticles BB = apply<DecayedParticles>(event, "BB");
47 // loop over particles
48 for (unsigned int ix=0; ix<BB.decaying().size(); ++ix) {
49 int imode=0, sign=1, idOther=22;
50 if (BB.decaying()[ix].abspid()==521) {
51 _c[0]->fill();
52 if (BB.modeMatches(ix,3,mode1)) {
53 imode= 0;
54 sign = 1;
55 }
56 else if (BB.modeMatches(ix,3,mode1CC)) {
57 imode= 0;
58 sign =-1;
59 }
60 else if (BB.modeMatches(ix,3,mode2)) {
61 imode= 1;
62 sign = 1;
63 idOther= 111;
64 }
65 else if (BB.modeMatches(ix,3,mode2CC)) {
66 imode= 1;
67 sign =-1;
68 idOther= 111;
69 }
70 else continue;
71 }
72 else {
73 _c[1]->fill();
74 if (BB.modeMatches(ix,3,mode3)) {
75 imode= 2;
76 sign = 1;
77 idOther=-211;
78 }
79 else if (BB.modeMatches(ix,3,mode3CC)) {
80 imode= 2;
81 sign =-1;
82 idOther= 211;
83 }
84 else continue;
85 }
86 const Particle& pp = BB.decayProducts()[ix].at( sign*2212)[0];
87 const Particle& lbar = BB.decayProducts()[ix].at(-sign*3122)[0];
88 const Particle& other = BB.decayProducts()[ix].at(idOther)[0];
89 FourMomentum pbaryon = pp.mom()+lbar.mom();
90 double mass = pbaryon.mass();
91 _h_mass[imode]->fill(mass);
92 // boost to B rest frame
93 LorentzTransform boost =
94 LorentzTransform::mkFrameTransformFromBeta(BB.decaying()[ix]. mom().betaVec());
95 FourMomentum pLam = boost.transform(lbar.mom());
96 pbaryon = boost.transform(pbaryon);
97 FourMomentum pProton = boost.transform(pp.mom());
98 _h_E[imode][0]->fill(pLam.E());
99 _h_E[imode][1]->fill();
100 if (mass<2.8) {
101 Vector3 axis = boost.transform(other.mom()).p3().unit();
102 LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(pbaryon.betaVec());
103 double cosp = axis.dot(boost1.transform(pProton).p3().unit());
104 _h_cosp[imode]->fill(cosp);
105 }
106 // finally the alpha parameter
107 // Lambda decay products
108 if (lbar.children().size()!=2) continue;
109 Particle pbar;
110 if (lbar.children()[0].pid()==-2212 &&
111 lbar.children()[1].pid()== 211) {
112 pbar = lbar.children()[0];
113 }
114 else if (lbar.children()[1].pid()==-sign*2212 &&
115 lbar.children()[0].pid()== sign*211) {
116 pbar = lbar.children()[1];
117 }
118 else {
119 continue;
120 }
121 LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pLam.betaVec());
122 Vector3 axis1 = - boost2.transform(boost.transform(BB.decaying()[ix].mom())).p3().unit();
123 Vector3 axis2 = - boost2.transform(boost.transform(pbar.mom())).p3().unit();
124 double cTheta = axis1.dot(axis2);
125 _h_alpha[imode][0]->fill(1.5*cTheta);
126 _h_alpha[imode][1]->fill();
127 }
128 }
129
130
131 /// Normalise histograms etc., after the run
132 void finalize() {
133 normalize(_h_cosp, 1.0, false);
134 scale(_h_mass[0],1e6/ *_c[0]);
135 scale(_h_mass[1],1e6/ *_c[0]);
136 scale(_h_mass[2],1e6/ *_c[1]);
137 for(unsigned int ix=0;ix<3;++ix) {
138 scale(_h_alpha[ix][0], 1./ *_h_alpha[ix][1]);
139 scale(_h_E [ix][0], 1./ *_h_E [ix][1]);
140 }
141 }
142
143 /// @}
144
145
146 /// @name Histograms
147 /// @{
148 Histo1DPtr _h_mass[3],_h_cosp[3];
149 CounterPtr _h_alpha[3][2],_h_E[3][2];
150 CounterPtr _c[2];
151 const map<PdgId,unsigned int> mode1 = { { 2212,1}, {-3122,1}, { 22,1} };
152 const map<PdgId,unsigned int> mode1CC = { {-2212,1}, { 3122,1}, { 22,1} };
153 const map<PdgId,unsigned int> mode2 = { { 2212,1}, {-3122,1}, { 111,1} };
154 const map<PdgId,unsigned int> mode2CC = { {-2212,1}, { 3122,1}, { 111,1} };
155 const map<PdgId,unsigned int> mode3 = { { 2212,1}, {-3122,1}, {-211,1} };
156 const map<PdgId,unsigned int> mode3CC = { {-2212,1}, { 3122,1}, { 211,1} };
157 /// @}
158
159
160 };
161
162
163 RIVET_DECLARE_PLUGIN(BELLE_2007_I748975);
164
165}
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