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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 | ||
288a4024 | 52 | const char* AliPID::fgkParticleName[AliPID::kSPECIESN+AliPID::kSPECIESLN+1] = { |
304864ab | 53 | "electron", |
54 | "muon", | |
55 | "pion", | |
56 | "kaon", | |
57 | "proton", | |
58 | "photon", | |
59 | "pi0", | |
60 | "neutron", | |
61 | "kaon0", | |
62 | "eleCon", | |
288a4024 | 63 | "deuteron", |
64 | "triton", | |
65 | "helium-3", | |
66 | "alpha", | |
304864ab | 67 | "unknown" |
68 | }; | |
69 | ||
288a4024 | 70 | const char* AliPID::fgkParticleShortName[AliPID::kSPECIESN+AliPID::kSPECIESLN+1] = { |
91dbd0dc | 71 | "e", |
72 | "mu", | |
73 | "pi", | |
74 | "K", | |
75 | "p", | |
76 | "photon", | |
77 | "pi0", | |
78 | "n", | |
79 | "K0", | |
80 | "eleCon", | |
288a4024 | 81 | "d", |
82 | "t", | |
83 | "he3", | |
84 | "alpha", | |
91dbd0dc | 85 | "unknown" |
86 | }; | |
87 | ||
288a4024 | 88 | const char* AliPID::fgkParticleLatexName[AliPID::kSPECIESN+AliPID::kSPECIESLN+1] = { |
91dbd0dc | 89 | "e", |
90 | "#mu", | |
91 | "#pi", | |
92 | "K", | |
93 | "p", | |
94 | "#gamma", | |
95 | "#pi_{0}", | |
96 | "n", | |
97 | "K_{0}", | |
98 | "eleCon", | |
288a4024 | 99 | "d", |
100 | "t", | |
101 | "he3", | |
102 | "#alpha", | |
91dbd0dc | 103 | "unknown" |
104 | }; | |
105 | ||
288a4024 | 106 | const Int_t AliPID::fgkParticleCode[AliPID::kSPECIESN+AliPID::kSPECIESLN+1] = { |
304864ab | 107 | ::kElectron, |
108 | ::kMuonMinus, | |
109 | ::kPiPlus, | |
110 | ::kKPlus, | |
111 | ::kProton, | |
112 | ::kGamma, | |
113 | ::kPi0, | |
114 | ::kNeutron, | |
115 | ::kK0, | |
0133aa88 | 116 | ::kElectron, |
288a4024 | 117 | 1000010020, |
118 | 1000010030, | |
119 | 1000020030, | |
120 | 1000020040, | |
304864ab | 121 | 0 |
122 | }; | |
123 | ||
288a4024 | 124 | /*const*/ Float_t AliPID::fgkParticleMass[AliPID::kSPECIESN+AliPID::kSPECIESLN+1] = { |
125 | 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 | |
a9bbb414 | 126 | /* |
90e48c0c | 127 | M(kElectron), // electron |
128 | M(kMuon), // muon | |
129 | M(kPion), // pion | |
130 | M(kKaon), // kaon | |
131 | M(kProton), // proton | |
132 | M(kPhoton), // photon | |
133 | M(kPi0), // pi0 | |
134 | M(kNeutron), // neutron | |
135 | M(kKaon0), // kaon0 | |
136 | M(kEleCon), // electron conversion | |
288a4024 | 137 | M(kDeuteron), // deuteron |
138 | M(kTriton), // triton | |
139 | M(kHe3), // he3 | |
140 | M(kAlpha), // alpha | |
90e48c0c | 141 | 0.00000 // unknown |
a9bbb414 | 142 | */ |
90e48c0c | 143 | }; |
304864ab | 144 | |
145 | Double_t AliPID::fgPrior[kSPECIESN] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}; | |
146 | ||
147 | ||
148 | //_______________________________________________________________________ | |
90e48c0c | 149 | AliPID::AliPID() : |
150 | TObject(), | |
151 | fCharged(0) | |
304864ab | 152 | { |
a9bbb414 | 153 | // |
154 | // Default constructor | |
155 | // | |
156 | Init(); | |
157 | // set default values (= equal probabilities) | |
158 | for (Int_t i = 0; i < kSPECIESN; i++) | |
304864ab | 159 | fProbDensity[i] = 1./kSPECIESN; |
304864ab | 160 | } |
161 | ||
162 | //_______________________________________________________________________ | |
90e48c0c | 163 | AliPID::AliPID(const Double_t* probDensity, Bool_t charged) : |
164 | TObject(), | |
165 | fCharged(charged) | |
304864ab | 166 | { |
90e48c0c | 167 | // |
a9bbb414 | 168 | // Standard constructor |
90e48c0c | 169 | // |
a9bbb414 | 170 | Init(); |
171 | // set given probability densities | |
172 | for (Int_t i = 0; i < kSPECIES; i++) | |
304864ab | 173 | fProbDensity[i] = probDensity[i]; |
a9bbb414 | 174 | |
175 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
304864ab | 176 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); |
304864ab | 177 | } |
178 | ||
179 | //_______________________________________________________________________ | |
90e48c0c | 180 | AliPID::AliPID(const Float_t* probDensity, Bool_t charged) : |
181 | TObject(), | |
182 | fCharged(charged) | |
304864ab | 183 | { |
90e48c0c | 184 | // |
a9bbb414 | 185 | // Standard constructor |
90e48c0c | 186 | // |
a9bbb414 | 187 | Init(); |
188 | // set given probability densities | |
189 | for (Int_t i = 0; i < kSPECIES; i++) | |
304864ab | 190 | fProbDensity[i] = probDensity[i]; |
a9bbb414 | 191 | |
192 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
304864ab | 193 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); |
304864ab | 194 | } |
195 | ||
196 | //_______________________________________________________________________ | |
197 | AliPID::AliPID(const AliPID& pid) : | |
198 | TObject(pid), | |
199 | fCharged(pid.fCharged) | |
200 | { | |
90e48c0c | 201 | // |
202 | // copy constructor | |
203 | // | |
a9bbb414 | 204 | // We do not call init here, MUST already be done |
205 | for (Int_t i = 0; i < kSPECIESN; i++) | |
304864ab | 206 | fProbDensity[i] = pid.fProbDensity[i]; |
304864ab | 207 | } |
208 | ||
3088e2dd | 209 | //_______________________________________________________________________ |
210 | void AliPID::SetProbabilities(const Double_t* probDensity, Bool_t charged) | |
211 | { | |
212 | // | |
213 | // Set the probability densities | |
214 | // | |
215 | for (Int_t i = 0; i < kSPECIES; i++) | |
216 | fProbDensity[i] = probDensity[i]; | |
217 | ||
218 | for (Int_t i = kSPECIES; i < kSPECIESN; i++) | |
219 | fProbDensity[i] = ((charged) ? 0 : probDensity[i]); | |
220 | } | |
221 | ||
304864ab | 222 | //_______________________________________________________________________ |
223 | AliPID& AliPID::operator = (const AliPID& pid) | |
224 | { | |
225 | // assignment operator | |
226 | ||
227 | fCharged = pid.fCharged; | |
228 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
229 | fProbDensity[i] = pid.fProbDensity[i]; | |
230 | } | |
231 | return *this; | |
232 | } | |
233 | ||
a9bbb414 | 234 | //_______________________________________________________________________ |
235 | void AliPID::Init() | |
236 | { | |
237 | // | |
238 | // Initialise the masses | |
239 | // | |
240 | // Initialise only once... | |
288a4024 | 241 | if(!fgkParticleMass[0]) |
242 | for (Int_t i = 0; i < kSPECIESN + kSPECIESLN; i++) | |
374ef46b | 243 | fgkParticleMass[i] = M(i); |
a9bbb414 | 244 | } |
304864ab | 245 | |
246 | //_____________________________________________________________________________ | |
247 | Double_t AliPID::GetProbability(EParticleType iType, | |
248 | const Double_t* prior) const | |
249 | { | |
a9bbb414 | 250 | // |
251 | // Get the probability to be a particle of type "iType" | |
252 | // assuming the a priori probabilities "prior" | |
253 | // | |
304864ab | 254 | Double_t sum = 0.; |
255 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
256 | for (Int_t i = 0; i < nSpecies; i++) { | |
257 | sum += fProbDensity[i] * prior[i]; | |
258 | } | |
259 | if (sum <= 0) { | |
260 | AliError("Invalid probability densities or priors"); | |
261 | return -1; | |
262 | } | |
263 | return fProbDensity[iType] * prior[iType] / sum; | |
264 | } | |
265 | ||
266 | //_____________________________________________________________________________ | |
267 | Double_t AliPID::GetProbability(EParticleType iType) const | |
268 | { | |
269 | // get the probability to be a particle of type "iType" | |
270 | // assuming the globaly set a priori probabilities | |
271 | ||
272 | return GetProbability(iType, fgPrior); | |
273 | } | |
274 | ||
275 | //_____________________________________________________________________________ | |
276 | void AliPID::GetProbabilities(Double_t* probabilities, | |
277 | const Double_t* prior) const | |
278 | { | |
279 | // get the probabilities to be a particle of given type | |
280 | // assuming the a priori probabilities "prior" | |
281 | ||
282 | Double_t sum = 0.; | |
283 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
284 | for (Int_t i = 0; i < nSpecies; i++) { | |
285 | sum += fProbDensity[i] * prior[i]; | |
286 | } | |
287 | if (sum <= 0) { | |
288 | AliError("Invalid probability densities or priors"); | |
289 | for (Int_t i = 0; i < nSpecies; i++) probabilities[i] = -1; | |
290 | return; | |
291 | } | |
292 | for (Int_t i = 0; i < nSpecies; i++) { | |
293 | probabilities[i] = fProbDensity[i] * prior[i] / sum; | |
294 | } | |
295 | } | |
296 | ||
297 | //_____________________________________________________________________________ | |
298 | void AliPID::GetProbabilities(Double_t* probabilities) const | |
299 | { | |
300 | // get the probabilities to be a particle of given type | |
301 | // assuming the globaly set a priori probabilities | |
302 | ||
303 | GetProbabilities(probabilities, fgPrior); | |
304 | } | |
305 | ||
306 | //_____________________________________________________________________________ | |
307 | AliPID::EParticleType AliPID::GetMostProbable(const Double_t* prior) const | |
308 | { | |
309 | // get the most probable particle id hypothesis | |
310 | // assuming the a priori probabilities "prior" | |
311 | ||
312 | Double_t max = 0.; | |
313 | EParticleType id = kPion; | |
314 | Int_t nSpecies = ((fCharged) ? kSPECIES : kSPECIESN); | |
315 | for (Int_t i = 0; i < nSpecies; i++) { | |
316 | Double_t prob = fProbDensity[i] * prior[i]; | |
317 | if (prob > max) { | |
318 | max = prob; | |
319 | id = EParticleType(i); | |
320 | } | |
321 | } | |
322 | if (max == 0) { | |
323 | AliError("Invalid probability densities or priors"); | |
324 | } | |
325 | return id; | |
326 | } | |
327 | ||
328 | //_____________________________________________________________________________ | |
329 | AliPID::EParticleType AliPID::GetMostProbable() const | |
330 | { | |
331 | // get the most probable particle id hypothesis | |
332 | // assuming the globaly set a priori probabilities | |
333 | ||
334 | return GetMostProbable(fgPrior); | |
335 | } | |
336 | ||
337 | ||
338 | //_____________________________________________________________________________ | |
339 | void AliPID::SetPriors(const Double_t* prior, Bool_t charged) | |
340 | { | |
341 | // use the given priors as global a priori probabilities | |
342 | ||
343 | Double_t sum = 0; | |
344 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
345 | if (charged && (i >= kSPECIES)) { | |
346 | fgPrior[i] = 0; | |
347 | } else { | |
348 | if (prior[i] < 0) { | |
349 | AliWarningClass(Form("negative prior (%g) for %ss. " | |
350 | "Using 0 instead.", prior[i], | |
351 | fgkParticleName[i])); | |
352 | fgPrior[i] = 0; | |
353 | } else { | |
354 | fgPrior[i] = prior[i]; | |
355 | } | |
356 | } | |
357 | sum += prior[i]; | |
358 | } | |
359 | if (sum == 0) { | |
360 | AliWarningClass("all priors are zero."); | |
361 | } | |
362 | } | |
363 | ||
364 | //_____________________________________________________________________________ | |
365 | void AliPID::SetPrior(EParticleType iType, Double_t prior) | |
366 | { | |
367 | // use the given prior as global a priori probability for particles | |
368 | // of type "iType" | |
369 | ||
370 | if (prior < 0) { | |
371 | AliWarningClass(Form("negative prior (%g) for %ss. Using 0 instead.", | |
372 | prior, fgkParticleName[iType])); | |
373 | prior = 0; | |
374 | } | |
375 | fgPrior[iType] = prior; | |
376 | } | |
377 | ||
378 | ||
304864ab | 379 | //_____________________________________________________________________________ |
380 | AliPID& AliPID::operator *= (const AliPID& pid) | |
381 | { | |
382 | // combine this probability densities with the one of "pid" | |
383 | ||
384 | for (Int_t i = 0; i < kSPECIESN; i++) { | |
385 | fProbDensity[i] *= pid.fProbDensity[i]; | |
386 | } | |
387 | return *this; | |
388 | } | |
389 | ||
390 | //_____________________________________________________________________________ | |
391 | AliPID operator * (const AliPID& pid1, const AliPID& pid2) | |
392 | { | |
393 | // combine the two probability densities | |
394 | ||
395 | AliPID result; | |
396 | result *= pid1; | |
397 | result *= pid2; | |
398 | return result; | |
399 | } |