Belle II Software light-2406-ragdoll
DistanceTools.cc
1/**************************************************************************
2 * basf2 (Belle II Analysis Software Framework) *
3 * Author: The Belle II Collaboration *
4 * *
5 * See git log for contributors and copyright holders. *
6 * This file is licensed under LGPL-3.0, see LICENSE.md. *
7 **************************************************************************/
8
9
10#include <analysis/utility/DistanceTools.h>
11#include <framework/logging/Logger.h>
12#include "TMath.h"
13
14using namespace Belle2;
15
16
17ROOT::Math::XYZVector DistanceTools::poca(ROOT::Math::XYZVector const& trackPos, ROOT::Math::XYZVector const& trackP,
18 ROOT::Math::XYZVector const& vtxPos)
19{
20 ROOT::Math::XYZVector trackDir(trackP.Unit());
21 ROOT::Math::XYZVector r(vtxPos - trackPos);
22 return trackPos + r.Dot(trackDir) * trackDir;
23}
24
25B2Vector3D DistanceTools::trackToVtxVec(B2Vector3D const& trackPos, B2Vector3D const& trackP, B2Vector3D const& vtxPos)
26{
27 B2Vector3D trackDir(trackP.Unit());
28 B2Vector3D r(vtxPos - trackPos);
29 return r - (r.Dot(trackDir)) * trackDir;
30}
31
32double DistanceTools::trackToVtxDist(B2Vector3D const& trackPos, B2Vector3D const& trackP, B2Vector3D const& vtxPos)
33{
34 return trackToVtxVec(trackPos, trackP, vtxPos).Mag();
35}
36
38 TMatrixDSym const& trackPosCovMat, TMatrixDSym const& vtxPosCovMat)
39{
40 if (trackPosCovMat.GetNcols() != 3 || vtxPosCovMat.GetNcols() != 3) {
41 B2ERROR("in DistanceTools::trackToVtxCovmat, matrices must be of size 3");
42 return TMatrixDSym(3);
43 }
44
45 TMatrixDSym rCovMat(trackPosCovMat + vtxPosCovMat);
46 B2Vector3D trackDir(trackP.Unit());
47 //d_j = r_j - v_j * v_k r_k
48 //Jij = del_i d_j = delta_ij - v_i * v_j
49 //Since the vector of closest approach is a linear function of r, its
50 //propagation of errors is exact
51 TMatrixDSym Jacobian(3);
52 // Jacobian_ij = delta_ij -v(i)v(j)
53 for (int i(0); i < 3; ++i)
54 for (int j(0); j < 3; ++j)
55 Jacobian(i, j) = -trackDir(i) * trackDir(j);
56 for (int i(0); i < 3; ++i)
57 Jacobian(i, i) += 1;
58
59 return rCovMat.Similarity(Jacobian); //calculates J * rCovMat * J^T, and returns it
60
61}
62
63double DistanceTools::trackToVtxDistErr(B2Vector3D const& trackPos, B2Vector3D const& trackP, B2Vector3D const& vtxPos,
64 TMatrixDSym const& trackPosCovMat, TMatrixDSym const& vtxPosCovMat)
65{
66 TMatrixDSym covMat(trackToVtxCovmat(trackP, trackPosCovMat, vtxPosCovMat));
67 B2Vector3D dVec(trackToVtxVec(trackPos, trackP, vtxPos));
68 // n is the normalise vector in the direction of the POCA between the track and the vtx
69 B2Vector3D n((1. / dVec.Mag()) * dVec);
70
71 double ret(0);
72
73 //error on the distance computed as d^T * covMat * d
74 for (int i(0); i < 3; ++i)
75 for (int j(0); j < 3; ++j)
76 ret += n(i) * covMat(i, j) * n(j);
77
78 return TMath::Sqrt(ret);
79}
80
81
83{
84 return vtx2Pos - vtx1Pos;
85}
86
87double DistanceTools::vtxToVtxDist(B2Vector3D const& vtx1Pos, B2Vector3D const& vtx2Pos)
88{
89 return vtxToVtxVec(vtx1Pos, vtx2Pos).Mag();
90}
91
92TMatrixDSym DistanceTools::vtxToVtxCovMat(TMatrixDSym const& vtx1CovMat, TMatrixDSym const& vtx2CovMat)
93{
94 if (vtx1CovMat.GetNcols() != 3 || vtx2CovMat.GetNcols() != 3) {
95 B2ERROR("in DistanceTools::vtxToVtxCovMat, matrices must be of size 3");
96 return TMatrixDSym(3);
97 }
98
99 return vtx1CovMat + vtx2CovMat;
100}
101
102double DistanceTools::vtxToVtxDistErr(B2Vector3D const& vtx1Pos, B2Vector3D const& vtx2Pos,
103 TMatrixDSym const& vtx1CovMat, TMatrixDSym const& vtx2CovMat)
104{
105 TMatrixDSym covMat(vtxToVtxCovMat(vtx1CovMat, vtx2CovMat));
106 B2Vector3D dVec(vtxToVtxVec(vtx1Pos, vtx2Pos));
107 B2Vector3D n((1. / dVec.Mag()) * dVec);
108
109 double ret(0);
110
111 //error on the distance computed as d^T * covMat * d
112 for (int i(0); i < 3; ++i)
113 for (int j(0); j < 3; ++j)
114 ret += n(i) * covMat(i, j) * n(j);
115
116 return TMath::Sqrt(ret);
117}
118
DataType Mag() const
The magnitude (rho in spherical coordinate system).
Definition: B2Vector3.h:159
B2Vector3< DataType > Unit() const
Unit vector parallel to this.
Definition: B2Vector3.h:269
TMatrixDSym vtxToVtxCovMat(TMatrixDSym const &vtx1CovMat, TMatrixDSym const &vtx2CovMat)
Returns the covariance (error) matrix related to the vector linking two vertices.
ROOT::Math::XYZVector poca(ROOT::Math::XYZVector const &trackPos, ROOT::Math::XYZVector const &trackP, ROOT::Math::XYZVector const &vtxPos)
Returns the Point Of Closest Approach of a track to a vertex.
double trackToVtxDistErr(B2Vector3D const &trackPos, B2Vector3D const &trackP, B2Vector3D const &vtxPos, TMatrixDSym const &trackPosCovMat, TMatrixDSym const &vtxPosCovMat)
Returns the estimated uncertainty between a vertex and a track's point of closest approach to that ve...
double trackToVtxDist(B2Vector3D const &trackPos, B2Vector3D const &trackP, B2Vector3D const &vtxPos)
Returns the distance between a vertex and a track's point of closest approach to that vertex.
TMatrixDSym trackToVtxCovmat(B2Vector3D const &trackP, TMatrixDSym const &trackPosCovMat, TMatrixDSym const &vtxPosCovMat)
Returns the covariance (error) matrix of the 3D vector between a vertex and a track's point of closes...
double vtxToVtxDist(B2Vector3D const &vtx1Pos, B2Vector3D const &vtx2Pos)
Returns the distance between two vertices.
B2Vector3D trackToVtxVec(B2Vector3D const &trackPos, B2Vector3D const &trackP, B2Vector3D const &vtxPos)
Returns the 3D vector between a vertex and a track's point of closest approach to that vertex.
B2Vector3D vtxToVtxVec(B2Vector3D const &vtx1Pos, B2Vector3D const &vtx2Pos)
Returns the 3D vector between two vertices, ie vtxPos2 - vtxPos1.
double vtxToVtxDistErr(B2Vector3D const &vtx1Pos, B2Vector3D const &vtx2Pos, TMatrixDSym const &vtx1CovMat, TMatrixDSym const &vtx2CovMat)
Returns the estimated uncertainty on the distance between two vertices.
Abstract base class for different kinds of events.
Definition: ClusterUtils.h:24