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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 | ||
91dbd0dc | 66 | const char* AliPID::fgkParticleShortName[AliPID::kSPECIESN+1] = { |
67 | "e", | |
68 | "mu", | |
69 | "pi", | |
70 | "K", | |
71 | "p", | |
72 | "photon", | |
73 | "pi0", | |
74 | "n", | |
75 | "K0", | |
76 | "eleCon", | |
77 | "unknown" | |
78 | }; | |
79 | ||
80 | const char* AliPID::fgkParticleLatexName[AliPID::kSPECIESN+1] = { | |
81 | "e", | |
82 | "#mu", | |
83 | "#pi", | |
84 | "K", | |
85 | "p", | |
86 | "#gamma", | |
87 | "#pi_{0}", | |
88 | "n", | |
89 | "K_{0}", | |
90 | "eleCon", | |
91 | "unknown" | |
92 | }; | |
93 | ||
304864ab | 94 | const Int_t AliPID::fgkParticleCode[AliPID::kSPECIESN+1] = { |
95 | ::kElectron, | |
96 | ::kMuonMinus, | |
97 | ::kPiPlus, | |
98 | ::kKPlus, | |
99 | ::kProton, | |
100 | ::kGamma, | |
101 | ::kPi0, | |
102 | ::kNeutron, | |
103 | ::kK0, | |
0133aa88 | 104 | ::kElectron, |
304864ab | 105 | 0 |
106 | }; | |
107 | ||
a9bbb414 | 108 | /*const*/ Float_t AliPID::fgkParticleMass[AliPID::kSPECIESN+1] = { |
109 | 0,0,0,0,0,0,0,0,0,0,0 | |
110 | /* | |
90e48c0c | 111 | M(kElectron), // electron |
112 | M(kMuon), // muon | |
113 | M(kPion), // pion | |
114 | M(kKaon), // kaon | |
115 | M(kProton), // proton | |
116 | M(kPhoton), // photon | |
117 | M(kPi0), // pi0 | |
118 | M(kNeutron), // neutron | |
119 | M(kKaon0), // kaon0 | |
120 | M(kEleCon), // electron conversion | |
121 | 0.00000 // unknown | |
a9bbb414 | 122 | */ |
90e48c0c | 123 | }; |
304864ab | 124 | |
125 | Double_t AliPID::fgPrior[kSPECIESN] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; | |
126 | ||
127 | ||
128 | //_______________________________________________________________________ | |
90e48c0c | 129 | AliPID::AliPID() : |
130 | TObject(), | |
131 | fCharged(0) | |
304864ab | 132 | { |
a9bbb414 | 133 | // |
134 | // Default constructor | |
135 | // | |
136 | Init(); | |
137 | // set default values (= equal probabilities) | |
138 | for (Int_t i = 0; i < kSPECIESN; i++) | |
304864ab | 139 | fProbDensity[i] = 1./kSPECIESN; |
304864ab | 140 | } |
141 | ||
142 | //_______________________________________________________________________ | |
90e48c0c | 143 | AliPID::AliPID(const Double_t* probDensity, Bool_t charged) : |
144 | TObject(), | |
145 | fCharged(charged) | |
304864ab | 146 | { |
90e48c0c | 147 | // |
a9bbb414 | 148 | // Standard constructor |
90e48c0c | 149 | // |
a9bbb414 | 150 | Init(); |
151 | // set given probability densities | |
152 | for (Int_t i = 0; i < kSPECIES; i++) | |
304864ab | 153 | fProbDensity[i] = probDensity[i]; |
a9bbb414 | 154 | |
155 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
304864ab | 156 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); |
304864ab | 157 | } |
158 | ||
159 | //_______________________________________________________________________ | |
90e48c0c | 160 | AliPID::AliPID(const Float_t* probDensity, Bool_t charged) : |
161 | TObject(), | |
162 | fCharged(charged) | |
304864ab | 163 | { |
90e48c0c | 164 | // |
a9bbb414 | 165 | // Standard constructor |
90e48c0c | 166 | // |
a9bbb414 | 167 | Init(); |
168 | // set given probability densities | |
169 | for (Int_t i = 0; i < kSPECIES; i++) | |
304864ab | 170 | fProbDensity[i] = probDensity[i]; |
a9bbb414 | 171 | |
172 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
304864ab | 173 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); |
304864ab | 174 | } |
175 | ||
176 | //_______________________________________________________________________ | |
177 | AliPID::AliPID(const AliPID& pid) : | |
178 | TObject(pid), | |
179 | fCharged(pid.fCharged) | |
180 | { | |
90e48c0c | 181 | // |
182 | // copy constructor | |
183 | // | |
a9bbb414 | 184 | // We do not call init here, MUST already be done |
185 | for (Int_t i = 0; i < kSPECIESN; i++) | |
304864ab | 186 | fProbDensity[i] = pid.fProbDensity[i]; |
304864ab | 187 | } |
188 | ||
3088e2dd | 189 | //_______________________________________________________________________ |
190 | void AliPID::SetProbabilities(const Double_t* probDensity, Bool_t charged) | |
191 | { | |
192 | // | |
193 | // Set the probability densities | |
194 | // | |
195 | for (Int_t i = 0; i < kSPECIES; i++) | |
196 | fProbDensity[i] = probDensity[i]; | |
197 | ||
198 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
199 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); | |
200 | } | |
201 | ||
304864ab | 202 | //_______________________________________________________________________ |
203 | AliPID& AliPID::operator = (const AliPID& pid) | |
204 | { | |
205 | // assignment operator | |
206 | ||
207 | fCharged = pid.fCharged; | |
208 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
209 | fProbDensity[i] = pid.fProbDensity[i]; | |
210 | } | |
211 | return *this; | |
212 | } | |
213 | ||
a9bbb414 | 214 | //_______________________________________________________________________ |
215 | void AliPID::Init() | |
216 | { | |
217 | // | |
218 | // Initialise the masses | |
219 | // | |
220 | // Initialise only once... | |
221 | if(!fgkParticleMass[0]) | |
222 | for (Int_t i = 0; i < kSPECIESN; i++) | |
374ef46b | 223 | fgkParticleMass[i] = M(i); |
a9bbb414 | 224 | } |
304864ab | 225 | |
226 | //_____________________________________________________________________________ | |
227 | Double_t AliPID::GetProbability(EParticleType iType, | |
228 | const Double_t* prior) const | |
229 | { | |
a9bbb414 | 230 | // |
231 | // Get the probability to be a particle of type "iType" | |
232 | // assuming the a priori probabilities "prior" | |
233 | // | |
304864ab | 234 | Double_t sum = 0.; |
235 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
236 | for (Int_t i = 0; i < nSpecies; i++) { | |
237 | sum += fProbDensity[i] * prior[i]; | |
238 | } | |
239 | if (sum <= 0) { | |
240 | AliError("Invalid probability densities or priors"); | |
241 | return -1; | |
242 | } | |
243 | return fProbDensity[iType] * prior[iType] / sum; | |
244 | } | |
245 | ||
246 | //_____________________________________________________________________________ | |
247 | Double_t AliPID::GetProbability(EParticleType iType) const | |
248 | { | |
249 | // get the probability to be a particle of type "iType" | |
250 | // assuming the globaly set a priori probabilities | |
251 | ||
252 | return GetProbability(iType, fgPrior); | |
253 | } | |
254 | ||
255 | //_____________________________________________________________________________ | |
256 | void AliPID::GetProbabilities(Double_t* probabilities, | |
257 | const Double_t* prior) const | |
258 | { | |
259 | // get the probabilities to be a particle of given type | |
260 | // assuming the a priori probabilities "prior" | |
261 | ||
262 | Double_t sum = 0.; | |
263 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
264 | for (Int_t i = 0; i < nSpecies; i++) { | |
265 | sum += fProbDensity[i] * prior[i]; | |
266 | } | |
267 | if (sum <= 0) { | |
268 | AliError("Invalid probability densities or priors"); | |
269 | for (Int_t i = 0; i < nSpecies; i++) probabilities[i] = -1; | |
270 | return; | |
271 | } | |
272 | for (Int_t i = 0; i < nSpecies; i++) { | |
273 | probabilities[i] = fProbDensity[i] * prior[i] / sum; | |
274 | } | |
275 | } | |
276 | ||
277 | //_____________________________________________________________________________ | |
278 | void AliPID::GetProbabilities(Double_t* probabilities) const | |
279 | { | |
280 | // get the probabilities to be a particle of given type | |
281 | // assuming the globaly set a priori probabilities | |
282 | ||
283 | GetProbabilities(probabilities, fgPrior); | |
284 | } | |
285 | ||
286 | //_____________________________________________________________________________ | |
287 | AliPID::EParticleType AliPID::GetMostProbable(const Double_t* prior) const | |
288 | { | |
289 | // get the most probable particle id hypothesis | |
290 | // assuming the a priori probabilities "prior" | |
291 | ||
292 | Double_t max = 0.; | |
293 | EParticleType id = kPion; | |
294 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
295 | for (Int_t i = 0; i < nSpecies; i++) { | |
296 | Double_t prob = fProbDensity[i] * prior[i]; | |
297 | if (prob > max) { | |
298 | max = prob; | |
299 | id = EParticleType(i); | |
300 | } | |
301 | } | |
302 | if (max == 0) { | |
303 | AliError("Invalid probability densities or priors"); | |
304 | } | |
305 | return id; | |
306 | } | |
307 | ||
308 | //_____________________________________________________________________________ | |
309 | AliPID::EParticleType AliPID::GetMostProbable() const | |
310 | { | |
311 | // get the most probable particle id hypothesis | |
312 | // assuming the globaly set a priori probabilities | |
313 | ||
314 | return GetMostProbable(fgPrior); | |
315 | } | |
316 | ||
317 | ||
318 | //_____________________________________________________________________________ | |
319 | void AliPID::SetPriors(const Double_t* prior, Bool_t charged) | |
320 | { | |
321 | // use the given priors as global a priori probabilities | |
322 | ||
323 | Double_t sum = 0; | |
324 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
325 | if (charged && (i >= kSPECIES)) { | |
326 | fgPrior[i] = 0; | |
327 | } else { | |
328 | if (prior[i] < 0) { | |
329 | AliWarningClass(Form("negative prior (%g) for %ss. " | |
330 | "Using 0 instead.", prior[i], | |
331 | fgkParticleName[i])); | |
332 | fgPrior[i] = 0; | |
333 | } else { | |
334 | fgPrior[i] = prior[i]; | |
335 | } | |
336 | } | |
337 | sum += prior[i]; | |
338 | } | |
339 | if (sum == 0) { | |
340 | AliWarningClass("all priors are zero."); | |
341 | } | |
342 | } | |
343 | ||
344 | //_____________________________________________________________________________ | |
345 | void AliPID::SetPrior(EParticleType iType, Double_t prior) | |
346 | { | |
347 | // use the given prior as global a priori probability for particles | |
348 | // of type "iType" | |
349 | ||
350 | if (prior < 0) { | |
351 | AliWarningClass(Form("negative prior (%g) for %ss. Using 0 instead.", | |
352 | prior, fgkParticleName[iType])); | |
353 | prior = 0; | |
354 | } | |
355 | fgPrior[iType] = prior; | |
356 | } | |
357 | ||
358 | ||
304864ab | 359 | //_____________________________________________________________________________ |
360 | AliPID& AliPID::operator *= (const AliPID& pid) | |
361 | { | |
362 | // combine this probability densities with the one of "pid" | |
363 | ||
364 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
365 | fProbDensity[i] *= pid.fProbDensity[i]; | |
366 | } | |
367 | return *this; | |
368 | } | |
369 | ||
370 | //_____________________________________________________________________________ | |
371 | AliPID operator * (const AliPID& pid1, const AliPID& pid2) | |
372 | { | |
373 | // combine the two probability densities | |
374 | ||
375 | AliPID result; | |
376 | result *= pid1; | |
377 | result *= pid2; | |
378 | return result; | |
379 | } |