1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/Beam.hh"
#include "Rivet/Projections/FinalState.hh"
#include "Rivet/Projections/UnstableParticles.hh"
#include "Rivet/Projections/Thrust.hh"
#define I_KNOW_THE_INITIAL_QUARKS_PROJECTION_IS_DODGY_BUT_NEED_TO_USE_IT
#include "Rivet/Projections/InitialQuarks.hh"
namespace Rivet {
/// @brief Transverse Lambda polarization
class BELLE_2019_I1687566 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(BELLE_2019_I1687566);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(Beam(), "Beams");
const FinalState fs;
declare(fs, "FS");
declare(Thrust(fs),"Thrust");
declare(UnstableParticles(),"UFS");
declare(InitialQuarks(), "IQF");
// Book histograms
for(unsigned int ix=0;ix<4;++ix) {
book(_p_lam[ix] ,1,ix+1,1);
book(_p_bar[ix] ,1,ix+1,2);
book(_p_lam_pip[ix],2,ix+1,1);
book(_p_lam_pim[ix],2,ix+1,2);
book(_p_lam_Kp [ix],2,ix+1,3);
book(_p_lam_Km [ix],2,ix+1,4);
book(_p_bar_pip[ix],2,ix+1,5);
book(_p_bar_pim[ix],2,ix+1,6);
book(_p_bar_Kp [ix],2,ix+1,7);
book(_p_bar_Km [ix],2,ix+1,8);
}
book(_p_lam_inc ,3,1,1);
book(_p_lam_prompt,3,1,3);
book(_p_lam_sigma ,3,1,5);
book(_p_bar_inc ,3,1,2);
book(_p_bar_prompt,3,1,4);
book(_p_bar_sigma ,3,1,6);
}
/// Perform the per-event analysis
void analyze(const Event& event) {
static const double alpha=0.642;
static const double norm=3./alpha*100.;
// Get beams and average beam momentum
const ParticlePair& beams = apply<Beam>(event, "Beams").beams();
const double meanBeamMom = ( beams.first.p3().mod() +
beams.second.p3().mod() ) / 2.0;
int flavour = 0;
const InitialQuarks& iqf = apply<InitialQuarks>(event, "IQF");
// If we only have two quarks (qqbar), just take the flavour.
// If we have more than two quarks, look for the highest energetic q-qbar pair.
if (iqf.particles().size() == 2) {
flavour = iqf.particles().front().abspid();
}
else {
map<int, double> quarkmap;
for (const Particle& p : iqf.particles()) {
if (quarkmap[p.pid()] < p.E()) {
quarkmap[p.pid()] = p.E();
}
}
double maxenergy = 0.;
for (int i = 1; i <= 5; ++i) {
if (quarkmap[i]+quarkmap[-i] > maxenergy) {
flavour = i;
}
}
}
// thrust, to define an axis
const Thrust& thrust = apply<Thrust>(event, "Thrust");
const UnstableParticles& ufs = apply<UnstableParticles>(event, "UFS");
const FinalState & fs = apply<FinalState>(event, "FS");
if(thrust.thrust()<0.8)
vetoEvent;
for(const Particle & lambda : ufs.particles(Cuts::abspid==3122)) {
int sign = lambda.pid()/3122;
if(lambda.children().size()!=2) continue;
// look at the decay products
Particle proton,pion;
if(lambda.children()[0].pid()==sign*2212 &&
lambda.children()[1].pid()==-sign*211) {
proton = lambda.children()[0];
pion = lambda.children()[1];
}
else if(lambda.children()[1].pid()==sign*2212 &&
lambda.children()[0].pid()==-sign*211) {
proton = lambda.children()[1];
pion = lambda.children()[0];
}
else
continue;
double xE = lambda.momentum().t()/meanBeamMom;
if(xE<0.2 || xE>0.9) continue;
Vector3 axis1 = lambda.momentum().p3().unit();
// transverse polarization
Vector3 axis2;
if(lambda.momentum().p3().dot(thrust.thrustAxis())>=0.) {
axis2 = thrust.thrustAxis();
}
else {
axis2 =-thrust.thrustAxis();
}
Vector3 axis3 = axis2.cross(axis1).unit();
// boost to the lambda rest frame
LorentzTransform boost = LorentzTransform::mkFrameTransformFromBeta(lambda.momentum().betaVec());
FourMomentum pproton = boost.transform(proton.momentum());
int ibin=-1;
if(xE<=0.3)
ibin=0;
else if(xE<=0.4)
ibin=1;
else if(xE<=0.5)
ibin=2;
else if(xE<=0.9)
ibin=3;
double cTheta = axis3.dot(pproton.p3().unit())*norm;
double pT = sqrt(sqr(thrust.thrustMajorAxis().dot(lambda.momentum().p3()))+
sqr(thrust.thrustMinorAxis().dot(lambda.momentum().p3())));
bool prompt=true;
for(const Particle & parent : lambda.parents()) {
if(parent.abspid()==3212) {
prompt=false;
break;
}
}
// using thrust axis
if(sign>0) {
_p_lam_inc->fill(xE,cTheta);
_p_lam[ibin]->fill(pT,cTheta);
if(flavour<=3) {
if(prompt) _p_lam_prompt->fill(xE,cTheta);
else _p_lam_sigma ->fill(xE,cTheta);
}
}
else if(sign<0) {
_p_bar_inc->fill(xE,cTheta);
_p_bar[ibin]->fill(pT,cTheta);
if(flavour<=3) {
if(prompt) _p_bar_prompt->fill(xE,cTheta);
else _p_bar_sigma ->fill(xE,cTheta);
}
}
for(const Particle & p2 : fs.particles(Cuts::abspid==211 || Cuts::abspid==321) ) {
if(axis2.dot(p2.p3())>0.) continue;
double xH = p2.momentum().t()/meanBeamMom;
Vector3 axisH = p2.momentum().p3();
Vector3 axis4 = axisH.cross(axis1).unit();
double cTheta2 = axis3.dot(pproton.p3().unit())*norm;
if(sign>0) {
if(p2.pid()==211) _p_lam_pip[ibin]->fill(xH,cTheta2);
else if(p2.pid()==-211) _p_lam_pim[ibin]->fill(xH,cTheta2);
else if(p2.pid()== 321) _p_lam_Kp [ibin]->fill(xH,cTheta2);
else if(p2.pid()==-321) _p_lam_Km [ibin]->fill(xH,cTheta2);
}
else {
if(p2.pid()==211) _p_bar_pip[ibin]->fill(xH,cTheta2);
else if(p2.pid()==-211) _p_bar_pim[ibin]->fill(xH,cTheta2);
else if(p2.pid()== 321) _p_bar_Kp [ibin]->fill(xH,cTheta2);
else if(p2.pid()==-321) _p_bar_Km [ibin]->fill(xH,cTheta2);
}
}
}
}
/// Normalise histograms etc., after the run
void finalize() {
}
//@}
/// @name Histograms
//@{
Profile1DPtr _p_lam[4],_p_bar[4];
Profile1DPtr _p_lam_pip[4],_p_lam_pim[4],_p_lam_Kp[4],_p_lam_Km[4];
Profile1DPtr _p_bar_pip[4],_p_bar_pim[4],_p_bar_Kp[4],_p_bar_Km[4];
Profile1DPtr _p_lam_inc,_p_lam_prompt,_p_lam_sigma;
Profile1DPtr _p_bar_inc,_p_bar_prompt,_p_bar_sigma;
//@}
};
// The hook for the plugin system
RIVET_DECLARE_PLUGIN(BELLE_2019_I1687566);
}
|