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f826d409 | 1 | //--------------------------------------------------------------------------------- |
2 | // The AliKFParticleBase class | |
3 | // . | |
4 | // @author S.Gorbunov, I.Kisel | |
5 | // @version 1.0 | |
6 | // @since 13.05.07 | |
7 | // | |
8 | // Class to reconstruct and store the decayed particle parameters. | |
9 | // The method is described in CBM-SOFT note 2007-003, | |
10 | // ``Reconstruction of decayed particles based on the Kalman filter'', | |
11 | // http://www.gsi.de/documents/DOC-2007-May-14-1.pdf | |
12 | // | |
13 | // This class describes general mathematics which is used by AliKFParticle class | |
14 | // | |
15 | // -= Copyright © ALICE HLT Group =- | |
16 | //_________________________________________________________________________________ | |
17 | ||
18 | ||
19 | ||
20 | #ifndef ALIKFPARTICLEBASE_H | |
21 | #define ALIKFPARTICLEBASE_H | |
22 | ||
23 | #include "TObject.h" | |
24 | ||
25 | class AliKFParticleBase :public TObject { | |
26 | ||
27 | public: | |
28 | ||
29 | //* | |
30 | //* ABSTRACT METHODS HAVE TO BE DEFINED IN USER CLASS | |
31 | //* | |
32 | ||
33 | //* Virtual method to access the magnetic field | |
34 | ||
35 | virtual void GetFieldValue(const Double_t xyz[], Double_t B[]) const = 0; | |
36 | ||
37 | //* Virtual methods needed for particle transportation | |
38 | //* One can use particular implementations for collider (only Bz component) | |
39 | //* geometry and for fixed-target (CBM-like) geometry which are provided below | |
40 | //* in TRANSPORT section | |
41 | ||
42 | //* Get dS to xyz[] space point | |
43 | ||
44 | virtual Double_t GetDStoPoint( const Double_t xyz[] ) const = 0; | |
45 | ||
46 | //* Get dS to other particle p (dSp for particle p also returned) | |
47 | ||
48 | virtual void GetDStoParticle( const AliKFParticleBase &p, | |
49 | Double_t &DS, Double_t &DSp ) const = 0; | |
50 | ||
51 | //* Transport on dS value along trajectory, output to P,C | |
52 | ||
53 | virtual void Transport( Double_t dS, Double_t P[], Double_t C[] ) const = 0; | |
54 | ||
55 | ||
56 | ||
57 | //* | |
58 | //* INITIALIZATION | |
59 | //* | |
60 | ||
61 | //* Constructor | |
62 | ||
63 | AliKFParticleBase(); | |
64 | ||
65 | //* Destructor | |
66 | ||
67 | virtual ~AliKFParticleBase(){}; | |
68 | ||
69 | //* Initialise covariance matrix and set current parameters to 0.0 | |
70 | ||
71 | void Initialize(); | |
72 | ||
73 | //* Set decay vertex parameters for linearisation | |
74 | ||
75 | void SetVtxGuess( Double_t x, Double_t y, Double_t z ); | |
76 | ||
77 | //* | |
78 | //* ACCESSORS | |
79 | //* | |
80 | ||
81 | //* Simple accessors | |
82 | ||
83 | Double_t GetX () const { return fP[0]; } | |
84 | Double_t GetY () const { return fP[1]; } | |
85 | Double_t GetZ () const { return fP[2]; } | |
86 | Double_t GetPx () const { return fP[3]; } | |
87 | Double_t GetPy () const { return fP[4]; } | |
88 | Double_t GetPz () const { return fP[5]; } | |
89 | Double_t GetE () const { return fP[6]; } | |
90 | Double_t GetS () const { return fP[7]; } | |
91 | Int_t GetQ () const { return fQ; } | |
92 | Double_t GetChi2 () const { return fChi2; } | |
93 | Int_t GetNDF () const { return fNDF; } | |
94 | ||
95 | Double_t GetParameter ( Int_t i ) const { return fP[i]; } | |
96 | Double_t GetCovariance( Int_t i ) const { return fC[i]; } | |
97 | Double_t GetCovariance( Int_t i, Int_t j ) const { return fC[IJ(i,j)]; } | |
98 | ||
99 | //* Accessors with calculations( &value, &estimated sigma ) | |
100 | //* error flag returned (0 means no error during calculations) | |
101 | ||
102 | Int_t GetMomentum ( Double_t &P, Double_t &SigmaP ) const ; | |
103 | Int_t GetMass ( Double_t &M, Double_t &SigmaM ) const ; | |
104 | Int_t GetDecayLength ( Double_t &L, Double_t &SigmaL ) const ; | |
105 | Int_t GetLifeTime ( Double_t &T, Double_t &SigmaT ) const ; | |
106 | ||
107 | //* | |
108 | //* MODIFIERS | |
109 | //* | |
110 | ||
111 | Double_t & X () { return fP[0]; } | |
112 | Double_t & Y () { return fP[1]; } | |
113 | Double_t & Z () { return fP[2]; } | |
114 | Double_t & Px () { return fP[3]; } | |
115 | Double_t & Py () { return fP[4]; } | |
116 | Double_t & Pz () { return fP[5]; } | |
117 | Double_t & E () { return fP[6]; } | |
118 | Double_t & S () { return fP[7]; } | |
119 | Int_t & Q () { return fQ; } | |
120 | Double_t & Chi2 () { return fChi2; } | |
121 | Int_t & NDF () { return fNDF; } | |
122 | ||
123 | Double_t & Parameter ( Int_t i ) { return fP[i]; } | |
124 | Double_t & Covariance( Int_t i ) { return fC[i]; } | |
125 | Double_t & Covariance( Int_t i, Int_t j ) { return fC[IJ(i,j)]; } | |
126 | ||
127 | ||
128 | //* | |
129 | //* CONSTRUCTION OF THE PARTICLE BY ITS DAUGHTERS AND MOTHER | |
130 | //* USING THE KALMAN FILTER METHOD | |
131 | //* | |
132 | ||
133 | ||
134 | //* Simple way to add daughter ex. D0+= Pion; | |
135 | ||
136 | void operator +=( const AliKFParticleBase &Daughter ); | |
137 | ||
138 | //* Add daughter track to the particle | |
139 | ||
140 | void AddDaughter( const AliKFParticleBase &Daughter ); | |
141 | ||
142 | //* Set production vertex | |
143 | ||
144 | void SetProductionVertex( const AliKFParticleBase &Vtx ); | |
145 | ||
146 | //* Set hard mass constraint | |
147 | ||
148 | void SetMassConstraint( Double_t Mass ); | |
149 | ||
150 | //* Everything in one go | |
151 | ||
152 | void Construct( const AliKFParticleBase *vDaughters[], Int_t NDaughters, | |
153 | const AliKFParticleBase *ProdVtx=0, Double_t Mass=-1 ); | |
154 | ||
155 | ||
156 | //* | |
157 | //* TRANSPORT | |
158 | //* | |
159 | //* ( main transportation parameter is S = SignedPath/Momentum ) | |
160 | //* ( parameters of decay & production vertices are stored locally ) | |
161 | //* | |
162 | ||
163 | ||
164 | //* Transport the particle to its decay vertex | |
165 | ||
166 | void TransportToDecayVertex(); | |
167 | ||
168 | //* Transport the particle to its production vertex | |
169 | ||
170 | void TransportToProductionVertex(); | |
171 | ||
172 | //* Transport the particle on dS parameter (SignedPath/Momentum) | |
173 | ||
174 | void TransportToDS( Double_t dS ); | |
175 | ||
176 | //* Particular extrapolators one can use | |
177 | ||
178 | Double_t GetDStoPointBz( Double_t Bz, const Double_t xyz[] ) const; | |
179 | ||
180 | void GetDStoParticleBz( Double_t Bz, const AliKFParticleBase &p, | |
181 | Double_t &dS, Double_t &dS1 ) const ; | |
182 | ||
183 | // Double_t GetDStoPointCBM( const Double_t xyz[] ) const; | |
184 | ||
185 | void TransportBz( Double_t Bz, Double_t dS, Double_t P[], Double_t C[] ) const; | |
186 | void TransportCBM( Double_t dS, Double_t P[], Double_t C[] ) const; | |
187 | ||
188 | ||
189 | //* | |
190 | //* OTHER UTILITIES | |
191 | //* | |
192 | ||
193 | //* Calculate distance from another object [cm] | |
194 | ||
195 | Double_t GetDistanceFromVertex( const Double_t vtx[] ) const; | |
196 | Double_t GetDistanceFromVertex( const AliKFParticleBase &Vtx ) const; | |
197 | Double_t GetDistanceFromParticleBz( Double_t Bz, | |
198 | const AliKFParticleBase &p ) const; | |
199 | ||
200 | //* Calculate sqrt(Chi2/ndf) deviation from vertex | |
201 | //* v = [xyz], Cv=[Cxx,Cxy,Cyy,Cxz,Cyz,Czz]-covariance matrix | |
202 | ||
203 | Double_t GetDeviationFromVertex( const Double_t v[], | |
204 | const Double_t Cv[]=0 ) const; | |
205 | Double_t GetDeviationFromVertex( const AliKFParticleBase &Vtx ) const; | |
206 | Double_t GetDeviationFromParticleBz( Double_t Bz, | |
207 | const AliKFParticleBase &p ) const; | |
208 | ||
209 | //* Subtract the particle from the vertex | |
210 | ||
211 | void SubtractFromVertex( Double_t v[], Double_t Cv[], | |
212 | Double_t &vChi2, Int_t vNDF ) const ; | |
213 | ||
214 | protected: | |
215 | ||
216 | static Int_t IJ( Int_t i, Int_t j ){ | |
217 | return ( j<=i ) ? i*(i+1)/2+j :j*(j+1)/2+i; | |
218 | } | |
219 | ||
220 | Double_t & Cij( Int_t i, Int_t j ){ return fC[IJ(i,j)]; } | |
221 | ||
222 | void Convert( bool ToProduction ); | |
223 | void TransportLine( Double_t S, Double_t P[], Double_t C[] ) const ; | |
224 | Double_t GetDStoPointLine( const Double_t xyz[] ) const; | |
225 | ||
226 | static void MultQSQt( const Double_t Q[], const Double_t S[], | |
227 | Double_t SOut[] ); | |
228 | ||
229 | ||
230 | Double_t fP[8]; //* Main particle parameters {X,Y,Z,Px,Py,Pz,E,S[=DecayLength/P]} | |
231 | Double_t fC[36]; //* Low-triangle covariance matrix of fP | |
232 | Int_t fQ; //* Particle charge | |
233 | Int_t fNDF; //* Number of degrees of freedom | |
234 | Double_t fChi2; //* Chi^2 | |
235 | ||
236 | Double_t fSFromDecay; //* Distance from decay vertex to current position | |
237 | ||
238 | Bool_t fAtProductionVertex; //* Flag shows that the particle error along | |
239 | //* its trajectory is taken from production vertex | |
240 | ||
241 | Double_t fVtxGuess[3]; //* Guess for the position of the decay vertex | |
242 | //* ( used for linearisation of equations ) | |
243 | ||
244 | Bool_t fIsLinearized; //* Flag shows that the guess is present | |
245 | ||
246 | ClassDef( AliKFParticleBase, 1 ); | |
247 | }; | |
248 | ||
249 | #endif |