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304864ab | 1 | /************************************************************************** |
2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * | |
3 | * * | |
4 | * Author: The ALICE Off-line Project. * | |
5 | * Contributors are mentioned in the code where appropriate. * | |
6 | * * | |
7 | * Permission to use, copy, modify and distribute this software and its * | |
8 | * documentation strictly for non-commercial purposes is hereby granted * | |
9 | * without fee, provided that the above copyright notice appears in all * | |
10 | * copies and that both the copyright notice and this permission notice * | |
11 | * appear in the supporting documentation. The authors make no claims * | |
12 | * about the suitability of this software for any purpose. It is * | |
13 | * provided "as is" without express or implied warranty. * | |
14 | **************************************************************************/ | |
15 | ||
16 | /* $Id$ */ | |
17 | ||
18 | /////////////////////////////////////////////////////////////////////////////// | |
19 | // // | |
20 | // particle id probability densities // | |
21 | // // | |
22 | // The AliPID class stores the probability densities for the different // | |
23 | // particle type hypotheses electron, muon, pion, kaon, proton, photon, // | |
24 | // pi0, neutron, K0 and electron conversion. These probability densities // | |
25 | // are determined from the detector response functions. // | |
26 | // The * and *= operators are overloaded for AliPID to combine the PIDs // | |
27 | // from different detectors. // | |
28 | // // | |
29 | // The Bayesian probability to be a particle of a given type can be // | |
30 | // calculated from the probability densities, if the a priori probabilities // | |
31 | // (or abundences, concentrations) of particle species are known. These // | |
32 | // priors can be given as argument to the GetProbability or GetMostProbable // | |
33 | // method or they can be set globally by calling the static method // | |
34 | // SetPriors(). // | |
35 | // // | |
36 | // The implementation of this class is based on the note ... // | |
37 | // by Iouri Belikov and Karel Safarik. // | |
38 | // // | |
39 | /////////////////////////////////////////////////////////////////////////////// | |
40 | ||
a9bbb414 | 41 | #include <TClass.h> |
42 | #include <TDatabasePDG.h> | |
43 | #include <TPDGCode.h> | |
304864ab | 44 | |
304864ab | 45 | #include "AliLog.h" |
a9bbb414 | 46 | #include "AliPID.h" |
304864ab | 47 | |
90e48c0c | 48 | #define M(PID) TDatabasePDG::Instance()->GetParticle(fgkParticleCode[(PID)])->Mass() |
304864ab | 49 | |
50 | ClassImp(AliPID) | |
51 | ||
304864ab | 52 | const char* AliPID::fgkParticleName[AliPID::kSPECIESN+1] = { |
53 | "electron", | |
54 | "muon", | |
55 | "pion", | |
56 | "kaon", | |
57 | "proton", | |
58 | "photon", | |
59 | "pi0", | |
60 | "neutron", | |
61 | "kaon0", | |
62 | "eleCon", | |
63 | "unknown" | |
64 | }; | |
65 | ||
66 | const Int_t AliPID::fgkParticleCode[AliPID::kSPECIESN+1] = { | |
67 | ::kElectron, | |
68 | ::kMuonMinus, | |
69 | ::kPiPlus, | |
70 | ::kKPlus, | |
71 | ::kProton, | |
72 | ::kGamma, | |
73 | ::kPi0, | |
74 | ::kNeutron, | |
75 | ::kK0, | |
76 | ::kGamma, | |
77 | 0 | |
78 | }; | |
79 | ||
a9bbb414 | 80 | /*const*/ Float_t AliPID::fgkParticleMass[AliPID::kSPECIESN+1] = { |
81 | 0,0,0,0,0,0,0,0,0,0,0 | |
82 | /* | |
90e48c0c | 83 | M(kElectron), // electron |
84 | M(kMuon), // muon | |
85 | M(kPion), // pion | |
86 | M(kKaon), // kaon | |
87 | M(kProton), // proton | |
88 | M(kPhoton), // photon | |
89 | M(kPi0), // pi0 | |
90 | M(kNeutron), // neutron | |
91 | M(kKaon0), // kaon0 | |
92 | M(kEleCon), // electron conversion | |
93 | 0.00000 // unknown | |
a9bbb414 | 94 | */ |
90e48c0c | 95 | }; |
304864ab | 96 | |
97 | Double_t AliPID::fgPrior[kSPECIESN] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; | |
98 | ||
99 | ||
100 | //_______________________________________________________________________ | |
90e48c0c | 101 | AliPID::AliPID() : |
102 | TObject(), | |
103 | fCharged(0) | |
304864ab | 104 | { |
a9bbb414 | 105 | // |
106 | // Default constructor | |
107 | // | |
108 | Init(); | |
109 | // set default values (= equal probabilities) | |
110 | for (Int_t i = 0; i < kSPECIESN; i++) | |
304864ab | 111 | fProbDensity[i] = 1./kSPECIESN; |
304864ab | 112 | } |
113 | ||
114 | //_______________________________________________________________________ | |
90e48c0c | 115 | AliPID::AliPID(const Double_t* probDensity, Bool_t charged) : |
116 | TObject(), | |
117 | fCharged(charged) | |
304864ab | 118 | { |
90e48c0c | 119 | // |
a9bbb414 | 120 | // Standard constructor |
90e48c0c | 121 | // |
a9bbb414 | 122 | Init(); |
123 | // set given probability densities | |
124 | for (Int_t i = 0; i < kSPECIES; i++) | |
304864ab | 125 | fProbDensity[i] = probDensity[i]; |
a9bbb414 | 126 | |
127 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
304864ab | 128 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); |
304864ab | 129 | } |
130 | ||
131 | //_______________________________________________________________________ | |
90e48c0c | 132 | AliPID::AliPID(const Float_t* probDensity, Bool_t charged) : |
133 | TObject(), | |
134 | fCharged(charged) | |
304864ab | 135 | { |
90e48c0c | 136 | // |
a9bbb414 | 137 | // Standard constructor |
90e48c0c | 138 | // |
a9bbb414 | 139 | Init(); |
140 | // set given probability densities | |
141 | for (Int_t i = 0; i < kSPECIES; i++) | |
304864ab | 142 | fProbDensity[i] = probDensity[i]; |
a9bbb414 | 143 | |
144 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
304864ab | 145 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); |
304864ab | 146 | } |
147 | ||
148 | //_______________________________________________________________________ | |
149 | AliPID::AliPID(const AliPID& pid) : | |
150 | TObject(pid), | |
151 | fCharged(pid.fCharged) | |
152 | { | |
90e48c0c | 153 | // |
154 | // copy constructor | |
155 | // | |
a9bbb414 | 156 | // We do not call init here, MUST already be done |
157 | for (Int_t i = 0; i < kSPECIESN; i++) | |
304864ab | 158 | fProbDensity[i] = pid.fProbDensity[i]; |
304864ab | 159 | } |
160 | ||
161 | //_______________________________________________________________________ | |
162 | AliPID& AliPID::operator = (const AliPID& pid) | |
163 | { | |
164 | // assignment operator | |
165 | ||
166 | fCharged = pid.fCharged; | |
167 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
168 | fProbDensity[i] = pid.fProbDensity[i]; | |
169 | } | |
170 | return *this; | |
171 | } | |
172 | ||
a9bbb414 | 173 | //_______________________________________________________________________ |
174 | void AliPID::Init() | |
175 | { | |
176 | // | |
177 | // Initialise the masses | |
178 | // | |
179 | // Initialise only once... | |
180 | if(!fgkParticleMass[0]) | |
181 | for (Int_t i = 0; i < kSPECIESN; i++) | |
374ef46b | 182 | fgkParticleMass[i] = M(i); |
a9bbb414 | 183 | } |
304864ab | 184 | |
185 | //_____________________________________________________________________________ | |
186 | Double_t AliPID::GetProbability(EParticleType iType, | |
187 | const Double_t* prior) const | |
188 | { | |
a9bbb414 | 189 | // |
190 | // Get the probability to be a particle of type "iType" | |
191 | // assuming the a priori probabilities "prior" | |
192 | // | |
304864ab | 193 | Double_t sum = 0.; |
194 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
195 | for (Int_t i = 0; i < nSpecies; i++) { | |
196 | sum += fProbDensity[i] * prior[i]; | |
197 | } | |
198 | if (sum <= 0) { | |
199 | AliError("Invalid probability densities or priors"); | |
200 | return -1; | |
201 | } | |
202 | return fProbDensity[iType] * prior[iType] / sum; | |
203 | } | |
204 | ||
205 | //_____________________________________________________________________________ | |
206 | Double_t AliPID::GetProbability(EParticleType iType) const | |
207 | { | |
208 | // get the probability to be a particle of type "iType" | |
209 | // assuming the globaly set a priori probabilities | |
210 | ||
211 | return GetProbability(iType, fgPrior); | |
212 | } | |
213 | ||
214 | //_____________________________________________________________________________ | |
215 | void AliPID::GetProbabilities(Double_t* probabilities, | |
216 | const Double_t* prior) const | |
217 | { | |
218 | // get the probabilities to be a particle of given type | |
219 | // assuming the a priori probabilities "prior" | |
220 | ||
221 | Double_t sum = 0.; | |
222 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
223 | for (Int_t i = 0; i < nSpecies; i++) { | |
224 | sum += fProbDensity[i] * prior[i]; | |
225 | } | |
226 | if (sum <= 0) { | |
227 | AliError("Invalid probability densities or priors"); | |
228 | for (Int_t i = 0; i < nSpecies; i++) probabilities[i] = -1; | |
229 | return; | |
230 | } | |
231 | for (Int_t i = 0; i < nSpecies; i++) { | |
232 | probabilities[i] = fProbDensity[i] * prior[i] / sum; | |
233 | } | |
234 | } | |
235 | ||
236 | //_____________________________________________________________________________ | |
237 | void AliPID::GetProbabilities(Double_t* probabilities) const | |
238 | { | |
239 | // get the probabilities to be a particle of given type | |
240 | // assuming the globaly set a priori probabilities | |
241 | ||
242 | GetProbabilities(probabilities, fgPrior); | |
243 | } | |
244 | ||
245 | //_____________________________________________________________________________ | |
246 | AliPID::EParticleType AliPID::GetMostProbable(const Double_t* prior) const | |
247 | { | |
248 | // get the most probable particle id hypothesis | |
249 | // assuming the a priori probabilities "prior" | |
250 | ||
251 | Double_t max = 0.; | |
252 | EParticleType id = kPion; | |
253 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
254 | for (Int_t i = 0; i < nSpecies; i++) { | |
255 | Double_t prob = fProbDensity[i] * prior[i]; | |
256 | if (prob > max) { | |
257 | max = prob; | |
258 | id = EParticleType(i); | |
259 | } | |
260 | } | |
261 | if (max == 0) { | |
262 | AliError("Invalid probability densities or priors"); | |
263 | } | |
264 | return id; | |
265 | } | |
266 | ||
267 | //_____________________________________________________________________________ | |
268 | AliPID::EParticleType AliPID::GetMostProbable() const | |
269 | { | |
270 | // get the most probable particle id hypothesis | |
271 | // assuming the globaly set a priori probabilities | |
272 | ||
273 | return GetMostProbable(fgPrior); | |
274 | } | |
275 | ||
276 | ||
277 | //_____________________________________________________________________________ | |
278 | void AliPID::SetPriors(const Double_t* prior, Bool_t charged) | |
279 | { | |
280 | // use the given priors as global a priori probabilities | |
281 | ||
282 | Double_t sum = 0; | |
283 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
284 | if (charged && (i >= kSPECIES)) { | |
285 | fgPrior[i] = 0; | |
286 | } else { | |
287 | if (prior[i] < 0) { | |
288 | AliWarningClass(Form("negative prior (%g) for %ss. " | |
289 | "Using 0 instead.", prior[i], | |
290 | fgkParticleName[i])); | |
291 | fgPrior[i] = 0; | |
292 | } else { | |
293 | fgPrior[i] = prior[i]; | |
294 | } | |
295 | } | |
296 | sum += prior[i]; | |
297 | } | |
298 | if (sum == 0) { | |
299 | AliWarningClass("all priors are zero."); | |
300 | } | |
301 | } | |
302 | ||
303 | //_____________________________________________________________________________ | |
304 | void AliPID::SetPrior(EParticleType iType, Double_t prior) | |
305 | { | |
306 | // use the given prior as global a priori probability for particles | |
307 | // of type "iType" | |
308 | ||
309 | if (prior < 0) { | |
310 | AliWarningClass(Form("negative prior (%g) for %ss. Using 0 instead.", | |
311 | prior, fgkParticleName[iType])); | |
312 | prior = 0; | |
313 | } | |
314 | fgPrior[iType] = prior; | |
315 | } | |
316 | ||
317 | ||
304864ab | 318 | //_____________________________________________________________________________ |
319 | AliPID& AliPID::operator *= (const AliPID& pid) | |
320 | { | |
321 | // combine this probability densities with the one of "pid" | |
322 | ||
323 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
324 | fProbDensity[i] *= pid.fProbDensity[i]; | |
325 | } | |
326 | return *this; | |
327 | } | |
328 | ||
329 | //_____________________________________________________________________________ | |
330 | AliPID operator * (const AliPID& pid1, const AliPID& pid2) | |
331 | { | |
332 | // combine the two probability densities | |
333 | ||
334 | AliPID result; | |
335 | result *= pid1; | |
336 | result *= pid2; | |
337 | return result; | |
338 | } |