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
| // -*- C++ -*-
#include "Rivet/Analysis.hh"
#include "Rivet/Projections/UnstableParticles.hh"
namespace Rivet {
/// @brief Lambda_c -> Lambda e+ nu_e asymmetry
class CLEOII_1994_I371611 : public Analysis {
public:
/// Constructor
RIVET_DEFAULT_ANALYSIS_CTOR(CLEOII_1994_I371611);
/// @name Analysis methods
//@{
/// Book histograms and initialise projections before the run
void init() {
// Initialise and register projections
declare(UnstableParticles(), "UFS" );
// Book histograms
book(_h_Lambda, 1,1,1);
}
void findChildren(Particle parent, int sign, unsigned int & npart,
Particles & lambda, Particles & e, Particles & nu) {
for(const Particle & child : parent.children()) {
if(child.pid()==sign*PID::LAMBDA) {
lambda.push_back(child);
++npart;
}
else if(child.pid()==-sign*PID::EMINUS) {
e.push_back(child);
++npart;
}
else if(child.pid()==sign*PID::NU_E) {
nu.push_back(child);
++npart;
}
else if(!child.children().empty()) {
findChildren(child,sign,npart,lambda,e,nu);
}
else {
++npart;
}
}
}
/// Perform the per-event analysis
void analyze(const Event& event) {
// loop over Lambda_c baryons
for( const Particle& Lambdac : apply<UnstableParticles>(event, "UFS").particles(Cuts::abspid==4122)) {
int sign = Lambdac.pid()/4122;
Particles lambda,e,nu;
unsigned int npart(0);
findChildren(Lambdac,sign,npart,lambda,e,nu);
if(npart!=3 || lambda.size()!=1 || e.size()!=1 || nu.size()!=1) continue;
Particle baryon2;
if(lambda[0].children()[0].pid()== sign*2212 &&
lambda[0].children()[1].pid()== -sign*211) {
baryon2 = lambda[0].children()[0];
}
else if(lambda[0].children()[1].pid()== sign*2212 &&
lambda[0].children()[0].pid()== -sign*211) {
baryon2 = lambda[0].children()[1];
}
else
continue;
// first boost to the Lambdac rest frame
LorentzTransform boost1 = LorentzTransform::mkFrameTransformFromBeta(Lambdac.momentum().betaVec());
FourMomentum pbaryon1 = boost1.transform(lambda[0].momentum());
FourMomentum pbaryon2 = boost1.transform(baryon2 .momentum());
// to lambda rest frame
LorentzTransform boost2 = LorentzTransform::mkFrameTransformFromBeta(pbaryon1.betaVec());
Vector3 axis = pbaryon1.p3().unit();
FourMomentum pp = boost2.transform(pbaryon2);
// calculate angle
double cTheta = pp.p3().unit().dot(axis);
_h_Lambda->fill(cTheta);
}
}
pair<double,double> calcAlpha(Histo1DPtr hist) {
if(hist->numEntries()==0.) return make_pair(0.,0.);
double sum1(0.),sum2(0.);
for (auto bin : hist->bins() ) {
double Oi = bin.area();
if(Oi==0.) continue;
double ai = 0.5*(bin.xMax()-bin.xMin());
double bi = 0.5*ai*(bin.xMax()+bin.xMin());
double Ei = bin.areaErr();
sum1 += sqr(bi/Ei);
sum2 += bi/sqr(Ei)*(Oi-ai);
}
return make_pair(sum2/sum1,sqrt(1./sum1));
}
/// Normalise histograms etc., after the run
void finalize() {
// asymmetry
normalize(_h_Lambda);
Scatter2DPtr _h_alpha;
book(_h_alpha,2,1,1);
pair<double,double> alpha = calcAlpha(_h_Lambda);
_h_alpha->addPoint(0.5, alpha.first, make_pair(0.5,0.5), make_pair(alpha.second,alpha.second) );
}
//@}
/// @name Histograms
//@{
Histo1DPtr _h_Lambda;
//@}
};
RIVET_DECLARE_PLUGIN(CLEOII_1994_I371611);
}
|