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#include <TrackingTools/GeomPropagators/interface/AnalyticalImpactPointExtrapolator.h>
to the point of closest approach to vtx in 3D. It is slightly faster than the ImpactPointExtrapolator. The helix model is explicitely used in the determination of the target surface. This target surface is centered on vtx; the axes of the local coordinate system (x_loc, y_loc, z_loc) are z_loc // trajectory direction at impact point; x_loc normal to trajectory and along impact vector (impact point - vtx); y_loc forms a right-handed system with the other axes.
Definition at line 26 of file AnalyticalImpactPointExtrapolator.h.
| AnalyticalImpactPointExtrapolator::AnalyticalImpactPointExtrapolator | ( | const MagneticField * | field | ) |
constructor with default geometrical propagator
Definition at line 12 of file AnalyticalImpactPointExtrapolator.cc.
00012 : 00013 thePropagator(new AnalyticalPropagator(theField, anyDirection)), 00014 theField(field) 00015 {}
| AnalyticalImpactPointExtrapolator::AnalyticalImpactPointExtrapolator | ( | const Propagator & | propagator, | |
| const MagneticField * | field | |||
| ) |
constructor with alternative propagator
Definition at line 17 of file AnalyticalImpactPointExtrapolator.cc.
References anyDirection, and thePropagator.
00018 : 00019 thePropagator(propagator.clone()), 00020 theField(field) 00021 { 00022 thePropagator->setPropagationDirection(anyDirection); 00023 }
| TrajectoryStateOnSurface AnalyticalImpactPointExtrapolator::extrapolate | ( | const TrajectoryStateOnSurface | tsos, | |
| const GlobalPoint & | vtx | |||
| ) | const |
as above, but from TrajectoryStateOnSurface
Definition at line 36 of file AnalyticalImpactPointExtrapolator.cc.
References extrapolateFullState(), and TrajectoryStateOnSurface::isValid().
00038 { 00039 if ( tsos.isValid() ) return extrapolateFullState(tsos,vtx); 00040 else return tsos; 00041 }
| TrajectoryStateOnSurface AnalyticalImpactPointExtrapolator::extrapolate | ( | const FreeTrajectoryState & | fts, | |
| const GlobalPoint & | vtx | |||
| ) | const |
extrapolation from FreeTrajectoryState
Definition at line 26 of file AnalyticalImpactPointExtrapolator.cc.
References extrapolateSingleState().
00028 { 00029 // static TimingReport::Item& timer = detailedDetTimer("AnalyticalImpactPointExtrapolator"); 00030 // TimeMe t(timer,false); 00031 00032 return extrapolateSingleState(fts, vtx); 00033 }
| TrajectoryStateOnSurface AnalyticalImpactPointExtrapolator::extrapolateFullState | ( | const TrajectoryStateOnSurface | tsos, | |
| const GlobalPoint & | vertex | |||
| ) | const [private] |
extrapolation of (multi) TSOS
Definition at line 44 of file AnalyticalImpactPointExtrapolator.cc.
References TrajectoryStateOnSurface::components(), extrapolateSingleState(), TrajectoryStateOnSurface::freeTrajectoryState(), TrajectoryStateOnSurface::isValid(), TrajectoryStateOnSurface::surface(), and thePropagator.
Referenced by extrapolate().
00046 { 00047 // 00048 // first determine IP plane using propagation with (single) FTS 00049 // could be optimised (will propagate errors even if duplicated below) 00050 // 00051 TrajectoryStateOnSurface singleState = 00052 extrapolateSingleState(*tsos.freeTrajectoryState(),vertex); 00053 if ( !singleState.isValid() || tsos.components().size()==1 ) return singleState; 00054 // 00055 // propagate multiTsos to plane found above 00056 // 00057 return thePropagator->propagate(tsos,singleState.surface()); 00058 }
| TrajectoryStateOnSurface AnalyticalImpactPointExtrapolator::extrapolateSingleState | ( | const FreeTrajectoryState & | fts, | |
| const GlobalPoint & | vertex | |||
| ) | const [private] |
extrapolation of (single) FTS
Definition at line 61 of file AnalyticalImpactPointExtrapolator.cc.
References anyDirection, FreeTrajectoryState::charge(), FreeTrajectoryState::curvilinearError(), e, FreeTrajectoryState::hasError(), CurvilinearTrajectoryError::matrix(), FreeTrajectoryState::momentum(), p, FreeTrajectoryState::parameters(), GlobalTrajectoryParameters::position(), FreeTrajectoryState::position(), propagateWithHelix(), rho, rot, s, theField, FreeTrajectoryState::transverseCurvature(), and x.
Referenced by extrapolate(), and extrapolateFullState().
00063 { 00064 // 00065 // initialisation of position, momentum and transverse curvature 00066 // 00067 GlobalPoint x(fts.position()); 00068 GlobalVector p(fts.momentum()); 00069 double rho = fts.transverseCurvature(); 00070 // 00071 // Straight line approximation? |rho|<1.e-10 equivalent to ~ 1um 00072 // difference in transversal position at 10m. 00073 // 00074 double s(0); 00075 if( fabs(rho)<1.e-10 ) { 00076 GlobalVector dx(p.dot(vertex-x)/p.mag2()*p); 00077 x += dx; 00078 float sign = p.dot(dx); 00079 s = sign>0 ? dx.mag() : -dx.mag(); 00080 } 00081 // 00082 // Helix case 00083 // 00084 else { 00085 HelixLineExtrapolation::PositionType helixPos(x); 00086 HelixLineExtrapolation::DirectionType helixDir(p); 00087 IterativeHelixExtrapolatorToLine extrapolator(helixPos,helixDir,rho,anyDirection); 00088 if ( !propagateWithHelix(extrapolator,vertex,x,p,s) ) return TrajectoryStateOnSurface(); 00089 } 00090 // 00091 // Define target surface: origin on line, x_local from line 00092 // to helix at closest approach, z_local along the helix 00093 // and y_local to complete right-handed system 00094 // 00095 GlobalVector zLocal(p.unit()); 00096 GlobalVector yLocal(zLocal.cross(x-vertex).unit()); 00097 GlobalVector xLocal(yLocal.cross(zLocal)); 00098 Surface::RotationType rot(xLocal,yLocal,zLocal); 00099 PlaneBuilder::ReturnType surface = PlaneBuilder().plane(vertex,rot); 00100 // 00101 // Compute propagated state 00102 // 00103 GlobalTrajectoryParameters gtp(x,p,fts.charge(), theField); 00104 if (fts.hasError()) { 00105 // 00106 // compute jacobian 00107 // 00108 AnalyticalCurvilinearJacobian analyticalJacobian(fts.parameters(), gtp.position(), gtp.momentum(), s); 00109 CurvilinearTrajectoryError cte( ROOT::Math::Similarity( analyticalJacobian.jacobian(), 00110 fts.curvilinearError().matrix()) ); 00111 return TrajectoryStateOnSurface(gtp,cte,*surface); 00112 } 00113 else { 00114 // 00115 // return state without errors 00116 // 00117 return TrajectoryStateOnSurface(gtp,*surface); 00118 } 00119 }
| bool AnalyticalImpactPointExtrapolator::propagateWithHelix | ( | const IterativeHelixExtrapolatorToLine & | extrapolator, | |
| const GlobalPoint & | vertex, | |||
| GlobalPoint & | x, | |||
| GlobalVector & | p, | |||
| double & | s | |||
| ) | const [private] |
the actual propagation to a new point & momentum vector
Definition at line 122 of file AnalyticalImpactPointExtrapolator.cc.
References IterativeHelixExtrapolatorToLine::direction(), PV3DBase< T, PVType, FrameType >::mag(), Basic3DVector< T >::mag(), IterativeHelixExtrapolatorToLine::pathLength(), and IterativeHelixExtrapolatorToLine::position().
Referenced by extrapolateSingleState().
00124 { 00125 // 00126 // save absolute value of momentum 00127 // 00128 double pmag(p.mag()); 00129 // 00130 // get path length to solution 00131 // 00132 std::pair<bool,double> propResult = extrapolator.pathLength(vertex); 00133 if ( !propResult.first ) return false; 00134 s = propResult.second; 00135 // 00136 // get point and (normalised) direction from path length 00137 // 00138 HelixLineExtrapolation::PositionType xGen = extrapolator.position(s); 00139 HelixLineExtrapolation::DirectionType pGen = extrapolator.direction(s); 00140 // 00141 // Fix normalisation and convert back to GlobalPoint / GlobalVector 00142 // 00143 x = GlobalPoint(xGen); 00144 pGen *= pmag/pGen.mag(); 00145 p = GlobalVector(pGen); 00146 // 00147 return true; 00148 }
const MagneticField* AnalyticalImpactPointExtrapolator::theField [private] |
Definition at line 57 of file AnalyticalImpactPointExtrapolator.h.
Referenced by extrapolateSingleState().
Definition at line 56 of file AnalyticalImpactPointExtrapolator.h.
Referenced by AnalyticalImpactPointExtrapolator(), and extrapolateFullState().
1.5.4