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b9d9108c | 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 | //-----------------------------------------------------------------// | |
17 | // // | |
18 | // Implementation of the TOF PID class // | |
19 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch // | |
20 | // // | |
21 | //-----------------------------------------------------------------// | |
22 | ||
23 | #include "TMath.h" | |
24 | #include "AliLog.h" | |
25 | ||
26 | #include "AliESDtrack.h" | |
27 | #include "AliESDEvent.h" | |
28 | ||
29 | #include "AliTOFpidESD.h" | |
30 | ||
31 | ClassImp(AliTOFpidESD) | |
32 | ||
33 | //_________________________________________________________________________ | |
34 | AliTOFpidESD::AliTOFpidESD(): | |
35 | fSigma(0), | |
36 | fRange(0), | |
37 | fPmax(0), // zero at 0.5 GeV/c for pp | |
38 | fTime0(0) | |
39 | { | |
40 | } | |
41 | //_________________________________________________________________________ | |
42 | AliTOFpidESD::AliTOFpidESD(Double_t *param): | |
43 | fSigma(param[0]), | |
44 | fRange(param[1]), | |
45 | fPmax(0), // zero at 0.5 GeV/c for pp | |
46 | fTime0(0) | |
47 | { | |
48 | // | |
49 | // The main constructor | |
50 | // | |
51 | // | |
52 | ||
53 | //fPmax=TMath::Exp(-0.5*3*3)/fSigma; // ~3 sigma at 0.5 GeV/c for PbPb | |
54 | } | |
55 | ||
56 | //_________________________________________________________________________ | |
57 | Double_t | |
58 | AliTOFpidESD::GetMismatchProbability(Double_t p, Double_t mass) const { | |
59 | // | |
60 | // Returns the probability of mismatching | |
61 | // assuming 1/(p*beta)^2 scaling | |
62 | // | |
63 | const Double_t km=0.5; // "reference" momentum (GeV/c) | |
64 | ||
65 | Double_t ref2=km*km*km*km/(km*km + mass*mass);// "reference" (p*beta)^2 | |
66 | Double_t p2beta2=p*p*p*p/(p*p + mass*mass); | |
67 | ||
68 | return fPmax*ref2/p2beta2; | |
69 | } | |
70 | ||
71 | //_________________________________________________________________________ | |
72 | Int_t AliTOFpidESD::MakePID(AliESDEvent *event, Double_t timeZero) | |
73 | { | |
74 | // | |
75 | // This function calculates the "detector response" PID probabilities | |
76 | // Just for a bare hint... | |
77 | ||
78 | AliDebug(1,Form("TOF PID Parameters: Sigma (ps)= %f, Range= %f",fSigma,fRange)); | |
79 | AliDebug(1,"++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ \n"); | |
80 | ||
81 | fTime0=timeZero; | |
82 | return MakePID(event); | |
83 | } | |
84 | ||
85 | //_________________________________________________________________________ | |
86 | Int_t AliTOFpidESD::MakePID(AliESDEvent *event) | |
87 | { | |
88 | // | |
89 | // This function calculates the "detector response" PID probabilities | |
90 | // Just for a bare hint... | |
91 | ||
92 | Int_t ntrk=event->GetNumberOfTracks(); | |
93 | AliESDtrack **tracks=new AliESDtrack*[ntrk]; | |
94 | ||
95 | Int_t i; | |
96 | for (i=0; i<ntrk; i++) { | |
97 | AliESDtrack *t=event->GetTrack(i); | |
98 | tracks[i]=t; | |
99 | } | |
100 | ||
101 | for (i=0; i<ntrk; i++) { | |
102 | AliESDtrack *t=tracks[i]; | |
103 | if ((t->GetStatus()&AliESDtrack::kTOFout)==0) continue; | |
104 | if ((t->GetStatus()&AliESDtrack::kTIME)==0) continue; | |
105 | ||
106 | Double_t time[AliPID::kSPECIES]; | |
107 | if (!ExpectedSignals(t,time,AliPID::kSPECIES)) continue; | |
108 | Double_t sigma[AliPID::kSPECIES]; | |
109 | if (!ExpectedSigmas(t,sigma,AliPID::kSPECIES)) continue; | |
110 | ||
111 | AliDebug(2,Form("Expected TOF signals [ps]: %f %f %f %f %f", | |
112 | GetExpectedSignal(t,AliPID::kElectron), | |
113 | GetExpectedSignal(t,AliPID::kMuon), | |
114 | GetExpectedSignal(t,AliPID::kPion), | |
115 | GetExpectedSignal(t,AliPID::kKaon), | |
116 | GetExpectedSignal(t,AliPID::kProton) | |
117 | )); | |
118 | ||
119 | AliDebug(2,Form("Expected TOF std deviations [ps]: %f %f %f %f %f", | |
120 | GetExpectedSigma(t,AliPID::kElectron), | |
121 | GetExpectedSigma(t,AliPID::kMuon), | |
122 | GetExpectedSigma(t,AliPID::kPion), | |
123 | GetExpectedSigma(t,AliPID::kKaon), | |
124 | GetExpectedSigma(t,AliPID::kProton) | |
125 | )); | |
126 | ||
127 | AliDebug(2,Form("Expected TOF std deviations [number of expected sigmas]: %f %f %f %f %f", | |
128 | GetNumberOfSigmas(t,AliPID::kElectron), | |
129 | GetNumberOfSigmas(t,AliPID::kMuon), | |
130 | GetNumberOfSigmas(t,AliPID::kPion), | |
131 | GetNumberOfSigmas(t,AliPID::kKaon), | |
132 | GetNumberOfSigmas(t,AliPID::kProton) | |
133 | )); | |
134 | ||
135 | Double_t tof = t->GetTOFsignal() - fTime0; | |
136 | ||
137 | Double_t p[AliPID::kSPECIES]; | |
138 | Bool_t mismatch = kTRUE, heavy = kTRUE; | |
139 | for (Int_t j=0; j<AliPID::kSPECIES; j++) { | |
140 | Double_t sig = sigma[j]; | |
141 | if (TMath::Abs(tof-time[j]) > fRange*sig) { | |
142 | p[j] = TMath::Exp(-0.5*fRange*fRange)/sig; | |
143 | } else | |
144 | p[j] = TMath::Exp(-0.5*(tof-time[j])*(tof-time[j])/(sig*sig))/sig; | |
145 | ||
146 | // Check the mismatching | |
147 | Double_t mass = AliPID::ParticleMass(j); | |
148 | Double_t pm = GetMismatchProbability(t->GetP(),mass); | |
149 | if (p[j]>pm) mismatch = kFALSE; | |
150 | ||
151 | // Check for particles heavier than (AliPID::kSPECIES - 1) | |
152 | if (tof < (time[j] + fRange*sig)) heavy=kFALSE; | |
153 | ||
154 | } | |
155 | ||
156 | if (mismatch) | |
157 | for (Int_t j=0; j<AliPID::kSPECIES; j++) p[j]=1/AliPID::kSPECIES; | |
158 | ||
159 | t->SetTOFpid(p); | |
160 | ||
161 | if (heavy) t->ResetStatus(AliESDtrack::kTOFpid); | |
162 | ||
163 | } | |
164 | ||
165 | delete[] tracks; | |
166 | ||
167 | return 0; | |
168 | } | |
169 | ||
170 | //_________________________________________________________________________ | |
171 | Bool_t AliTOFpidESD::ExpectedSignals(const AliESDtrack *t, | |
172 | Double_t s[],Int_t n) const | |
173 | { | |
174 | // | |
175 | // Return the expected PID signals for the involved particle species | |
176 | // | |
177 | ||
178 | if (n > AliPID::kSPECIESN) return kFALSE; | |
179 | if ( !t->IsOn(AliESDtrack::kTIME) ) return kFALSE; | |
180 | ||
181 | Double_t time[AliPID::kSPECIESN]; | |
182 | t->GetIntegratedTimes(time); | |
183 | for (Int_t i=0; i<n; i++) s[i]=time[i]; | |
184 | return kTRUE; | |
185 | } | |
186 | ||
187 | //_________________________________________________________________________ | |
188 | Bool_t AliTOFpidESD::ExpectedSigmas(const AliESDtrack *t, | |
189 | Double_t s[],Int_t n) const | |
190 | { | |
191 | // | |
192 | // Return the expected sigma of PID signals for the involved | |
193 | // particle species. | |
194 | // This approximate (but reasonable) formula takes into account the | |
195 | // relative momentum resolution. | |
196 | // | |
197 | ||
198 | Double_t time[AliPID::kSPECIESN]; | |
199 | if ( !ExpectedSignals(t,time,n) ) return kFALSE; | |
200 | ||
201 | Double_t mom = t->GetP(); | |
202 | Double_t dpp = 0.01; //mean relative pt resolution; | |
203 | if (mom>0.5) dpp = 0.01*mom; | |
204 | for (Int_t i=0; i<n; i++) { | |
205 | Double_t mass = AliPID::ParticleMass(i); | |
206 | Double_t sigma = dpp*time[i]/(1.+ mom*mom/(mass*mass)); | |
207 | s[i] = TMath::Sqrt(sigma*sigma + fSigma*fSigma); | |
208 | } | |
209 | return kTRUE; | |
210 | } | |
211 | ||
212 | //_________________________________________________________________________ | |
213 | Bool_t AliTOFpidESD::NumberOfSigmas(const AliESDtrack *t, | |
214 | Double_t s[],Int_t n) const | |
215 | { | |
216 | // | |
217 | // Returns the deviation of the actual PID signal from the expected | |
218 | // signal, in units of expected sigmas. | |
219 | // | |
220 | ||
221 | Double_t time[AliPID::kSPECIESN]; | |
222 | if ( !ExpectedSignals(t,time,n) ) return kFALSE; | |
223 | ||
224 | if ( !ExpectedSigmas(t,s,n) ) return kFALSE; | |
225 | ||
226 | Double_t tof = t->GetTOFsignal() - fTime0; | |
227 | for (Int_t i=0; i<n; i++) s[i] = (time[i]-tof)/s[i]; | |
228 | ||
229 | return kTRUE; | |
230 | } | |
231 | ||
232 | //_________________________________________________________________________ | |
233 | Double_t AliTOFpidESD::GetExpectedSignal(const AliESDtrack *t, | |
234 | AliPID::EParticleType n) const | |
235 | { | |
236 | // | |
237 | // Return the expected PID signal for the specified particle type. | |
238 | // If the operation is not possible, return a negative value. | |
239 | // | |
240 | ||
241 | if (Int_t(n) >= AliPID::kSPECIESN) return -1.; | |
242 | if ( !t->IsOn(AliESDtrack::kTIME) ) return -1.; | |
243 | ||
244 | Double_t time[AliPID::kSPECIESN]; | |
245 | t->GetIntegratedTimes(time); | |
246 | ||
247 | return time[n]; | |
248 | } | |
249 | ||
250 | //_________________________________________________________________________ | |
251 | Double_t AliTOFpidESD::GetExpectedSigma(const AliESDtrack *t, | |
252 | AliPID::EParticleType n) const | |
253 | { | |
254 | // | |
255 | // Return the expected sigma of the PID signal for the specified | |
256 | // particle type. | |
257 | // If the operation is not possible, return a negative value. | |
258 | // | |
259 | ||
260 | Double_t time[AliPID::kSPECIESN]; | |
261 | if ( !ExpectedSignals(t,time,AliPID::kSPECIESN) ) return -1.; | |
262 | ||
263 | Double_t mom = t->GetP(); | |
264 | Double_t dpp = 0.01; //mean relative pt resolution; | |
265 | if (mom>0.5) dpp = 0.01*mom; | |
266 | ||
267 | Double_t mass = AliPID::ParticleMass(n); | |
268 | Double_t sigma = dpp*time[n]/(1.+ mom*mom/(mass*mass)); | |
269 | ||
270 | return TMath::Sqrt(sigma*sigma + fSigma*fSigma); | |
271 | } | |
272 | ||
273 | //_________________________________________________________________________ | |
274 | Double_t AliTOFpidESD::GetNumberOfSigmas(const AliESDtrack *t, | |
275 | AliPID::EParticleType n) const | |
276 | { | |
277 | // | |
278 | // Returns the deviation of the actual PID signal from the expected | |
279 | // signal for the specified particle type, in units of expected | |
280 | // sigmas. | |
281 | // If the operation is not possible, return a negative value. | |
282 | // | |
283 | ||
284 | Double_t time=GetExpectedSignal(t,n);; | |
285 | if (time < 0.) return -1.; | |
286 | ||
287 | Double_t sigma=GetExpectedSigma(t,n); | |
288 | if (sigma < 0.) return -1; | |
289 | ||
290 | Double_t tof=t->GetTOFsignal() - fTime0; | |
291 | return (time-tof)/sigma; | |
292 | } |