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10d100d4 | 1 | /************************************************************************** |
2 | * Copyright(c) 2005-2007, 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 | // ITS PID method # 1 | |
20 | // Implementation of the ITS PID class | |
21 | // Very naive one... Should be made better by the detector experts... | |
22 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch | |
23 | //----------------------------------------------------------------- | |
24 | #include "TMath.h" | |
25 | #include "AliITSPIDResponse.h" | |
26 | #include "AliITSPidParams.h" | |
27 | #include "AliExternalTrackParam.h" | |
28 | ||
10d100d4 | 29 | ClassImp(AliITSPIDResponse) |
30 | ||
15e979c9 | 31 | AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC): |
10d100d4 | 32 | fRes(0.13), |
33 | fKp1(15.77), | |
34 | fKp2(4.95), | |
35 | fKp3(0.312), | |
36 | fKp4(2.14), | |
37 | fKp5(0.82) | |
38 | { | |
15e979c9 | 39 | if(!isMC){ |
40 | fBBtpcits[0]=0.73; | |
41 | fBBtpcits[1]=14.68; | |
42 | fBBtpcits[2]=0.905; | |
43 | fBBtpcits[3]=1.2; | |
44 | fBBtpcits[4]=6.6; | |
62ccfebf | 45 | fBBsa[0]=2.73198E7; //pure PHOBOS parameterization |
88f46717 | 46 | fBBsa[1]=6.92389; |
47 | fBBsa[2]=1.90088E-6; | |
48 | fBBsa[3]=1.90088E-6; | |
49 | fBBsa[4]=3.40644E-7; | |
62ccfebf | 50 | fBBsaHybrid[0]=1.43505E7; //PHOBOS+Polinomial parameterization |
51 | fBBsaHybrid[1]=49.3402; | |
52 | fBBsaHybrid[2]=1.77741E-7; | |
53 | fBBsaHybrid[3]=1.77741E-7; | |
54 | fBBsaHybrid[4]=1.01311E-7; | |
55 | fBBsaHybrid[5]=77.2777; | |
56 | fBBsaHybrid[6]=33.4099; | |
57 | fBBsaHybrid[7]=46.0089; | |
58 | fBBsaHybrid[8]=-2.26583; | |
59 | fBBsaElectron[0]=4.05799E6; //electrons in the ITS | |
88f46717 | 60 | fBBsaElectron[1]=38.5713; |
61 | fBBsaElectron[2]=1.46462E-7; | |
62 | fBBsaElectron[3]=1.46462E-7; | |
63 | fBBsaElectron[4]=4.40284E-7; | |
8abeb05b | 64 | fResolSA[0]=1.; // 0 cluster tracks should not be used |
88f46717 | 65 | fResolSA[1]=0.25; // rough values for tracks with 1 |
66 | fResolSA[2]=0.131; // value from pp 2010 run (L. Milano, 16-Jun-11) | |
67 | fResolSA[3]=0.113; // value from pp 2010 run | |
8abeb05b | 68 | fResolSA[4]=0.104; // value from pp 2010 run |
15e979c9 | 69 | for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13; |
70 | }else{ | |
99daa709 | 71 | fBBtpcits[0]=1.04; |
72 | fBBtpcits[1]=27.14; | |
73 | fBBtpcits[2]=1.00; | |
74 | fBBtpcits[3]=0.964; | |
75 | fBBtpcits[4]=2.59; | |
62ccfebf | 76 | fBBsa[0]=2.02078E7; //pure PHOBOS parameterization |
88f46717 | 77 | fBBsa[1]=14.0724; |
78 | fBBsa[2]=3.84454E-7; | |
79 | fBBsa[3]=3.84454E-7; | |
80 | fBBsa[4]=2.43913E-7; | |
62ccfebf | 81 | fBBsaHybrid[0]=1.05381E7; //PHOBOS+Polinomial parameterization |
82 | fBBsaHybrid[1]=89.3933; | |
83 | fBBsaHybrid[2]=2.4831E-7; | |
84 | fBBsaHybrid[3]=2.4831E-7; | |
85 | fBBsaHybrid[4]=7.80591E-8; | |
86 | fBBsaHybrid[5]=62.9214; | |
87 | fBBsaHybrid[6]=32.347; | |
88 | fBBsaHybrid[7]=58.7661; | |
89 | fBBsaHybrid[8]=-3.39869; | |
90 | fBBsaElectron[0]=2.26807E6; //electrons in the ITS | |
88f46717 | 91 | fBBsaElectron[1]=99.985; |
92 | fBBsaElectron[2]=0.000714841; | |
93 | fBBsaElectron[3]=0.000259585; | |
94 | fBBsaElectron[4]=1.39412E-7; | |
8abeb05b | 95 | fResolSA[0]=1.; // 0 cluster tracks should not be used |
88f46717 | 96 | fResolSA[1]=0.25; // rough values for tracks with 1 |
97 | fResolSA[2]=0.126; // value from pp 2010 simulations (L. Milano, 16-Jun-11) | |
98 | fResolSA[3]=0.109; // value from pp 2010 simulations | |
99 | fResolSA[4]=0.097; // value from pp 2010 simulations | |
15e979c9 | 100 | for(Int_t i=0; i<5;i++) fResolTPCITS[i]=0.13; |
101 | } | |
10d100d4 | 102 | } |
103 | ||
56576f1e | 104 | /* |
10d100d4 | 105 | //_________________________________________________________________________ |
106 | AliITSPIDResponse::AliITSPIDResponse(Double_t *param): | |
9ebbddd4 | 107 | fRes(param[0]), |
10d100d4 | 108 | fKp1(15.77), |
109 | fKp2(4.95), | |
110 | fKp3(0.312), | |
111 | fKp4(2.14), | |
112 | fKp5(0.82) | |
113 | { | |
114 | // | |
115 | // The main constructor | |
116 | // | |
6b4634a4 | 117 | for (Int_t i=0; i<5;i++) { |
118 | fBBsa[i]=0.; | |
119 | fBBtpcits[i]=0.; | |
120 | fResolSA[i]=0.; | |
121 | fResolTPCITS[i]=0.; | |
122 | } | |
10d100d4 | 123 | } |
56576f1e | 124 | */ |
10d100d4 | 125 | |
8abeb05b | 126 | //_________________________________________________________________________ |
15e979c9 | 127 | Double_t AliITSPIDResponse::BetheAleph(Double_t p, Double_t mass) const { |
10d100d4 | 128 | // |
129 | // returns AliExternalTrackParam::BetheBloch normalized to | |
130 | // fgMIP at the minimum | |
131 | // | |
15e979c9 | 132 | |
10d100d4 | 133 | Double_t bb= |
134 | AliExternalTrackParam::BetheBlochAleph(p/mass,fKp1,fKp2,fKp3,fKp4,fKp5); | |
9ebbddd4 | 135 | return bb; |
10d100d4 | 136 | } |
137 | ||
8abeb05b | 138 | //_________________________________________________________________________ |
15e979c9 | 139 | Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const { |
140 | // | |
141 | // returns AliExternalTrackParam::BetheBloch normalized to | |
142 | // fgMIP at the minimum | |
143 | // | |
144 | ||
145 | Double_t bg=p/mass; | |
146 | Double_t beta = bg/TMath::Sqrt(1.+ bg*bg); | |
147 | Double_t gamma=bg/beta; | |
62ccfebf | 148 | Double_t bb=1.; |
149 | ||
15e979c9 | 150 | Double_t par[5]; |
151 | if(isSA){ | |
88f46717 | 152 | if(mass>0.0005 && mass<0.00052){ |
153 | //if is an electron use a specific BB parameterization | |
154 | //To be used only between 100 and 160 MeV/c | |
155 | for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip]; | |
156 | }else{ | |
157 | for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsa[ip]; | |
158 | } | |
15e979c9 | 159 | }else{ |
160 | for(Int_t ip=0; ip<5;ip++) par[ip]=fBBtpcits[ip]; | |
161 | } | |
162 | Double_t eff=1.0; | |
163 | if(bg<par[2]) | |
164 | eff=(bg-par[3])*(bg-par[3])+par[4]; | |
165 | else | |
166 | eff=(par[2]-par[3])*(par[2]-par[3])+par[4]; | |
88f46717 | 167 | |
15e979c9 | 168 | if(gamma>=0. && beta>0.){ |
169 | bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff; | |
170 | } | |
171 | return bb; | |
172 | } | |
173 | ||
62ccfebf | 174 | //_________________________________________________________________________ |
175 | Double_t AliITSPIDResponse::BetheITSsaHybrid(Double_t p, Double_t mass) const { | |
176 | // | |
177 | // returns AliExternalTrackParam::BetheBloch normalized to | |
178 | // fgMIP at the minimum. The PHOBOS parameterization is used for beta*gamma>0.76. | |
179 | // For beta*gamma<0.76 a polinomial function is used | |
180 | ||
181 | Double_t bg=p/mass; | |
182 | Double_t beta = bg/TMath::Sqrt(1.+ bg*bg); | |
183 | Double_t gamma=bg/beta; | |
184 | Double_t bb=1.; | |
185 | ||
186 | Double_t par[9]; | |
187 | //parameters for pi, K, p | |
188 | for(Int_t ip=0; ip<9;ip++) par[ip]=fBBsaHybrid[ip]; | |
189 | //if it is an electron the PHOBOS part of the parameterization is tuned for e | |
190 | //in the range used for identification beta*gamma is >0.76 for electrons | |
191 | //To be used only between 100 and 160 MeV/c | |
192 | if(mass>0.0005 && mass<0.00052)for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip]; | |
193 | ||
194 | if(gamma>=0. && beta>0. && bg>0.1){ | |
195 | if(bg>0.76){//PHOBOS | |
196 | Double_t eff=1.0; | |
197 | if(bg<par[2]) | |
198 | eff=(bg-par[3])*(bg-par[3])+par[4]; | |
199 | else | |
200 | eff=(par[2]-par[3])*(par[2]-par[3])+par[4]; | |
201 | ||
202 | bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff; | |
203 | }else{//Polinomial | |
204 | bb=par[5] + par[6]/bg + par[7]/(bg*bg) + par[8]/(bg*bg*bg); | |
205 | } | |
206 | } | |
207 | return bb; | |
208 | } | |
209 | ||
8abeb05b | 210 | //_________________________________________________________________________ |
15e979c9 | 211 | Double_t AliITSPIDResponse::GetResolution(Double_t bethe, |
212 | Int_t nPtsForPid, | |
213 | Bool_t isSA) const { | |
10d100d4 | 214 | // |
215 | // Calculate expected resolution for truncated mean | |
216 | // | |
15e979c9 | 217 | Float_t r; |
218 | if(isSA) r=fResolSA[nPtsForPid]; | |
219 | else r=fResolTPCITS[nPtsForPid]; | |
220 | return r*bethe; | |
10d100d4 | 221 | } |
222 | ||
15e979c9 | 223 | |
224 | ||
225 | ||
8abeb05b | 226 | //_________________________________________________________________________ |
b52bfc67 | 227 | void AliITSPIDResponse::GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES], Bool_t isMC) const { |
10d100d4 | 228 | // |
229 | // Method to calculate PID probabilities for a single track | |
230 | // using the likelihood method | |
231 | // | |
232 | const Int_t nLay = 4; | |
2ca1f4ee | 233 | const Int_t nPart= 4; |
10d100d4 | 234 | |
b52bfc67 | 235 | static AliITSPidParams pars(isMC); // Pid parametrisation parameters |
10d100d4 | 236 | |
2ca1f4ee | 237 | Double_t itsProb[nPart] = {1,1,1,1}; // e, p, K, pi |
10d100d4 | 238 | |
239 | for (Int_t iLay = 0; iLay < nLay; iLay++) { | |
2ca1f4ee | 240 | if (qclu[iLay] <= 50.) |
10d100d4 | 241 | continue; |
242 | ||
243 | Float_t dedx = qclu[iLay]; | |
244 | Float_t layProb = pars.GetLandauGausNorm(dedx,AliPID::kProton,mom,iLay+3); | |
245 | itsProb[0] *= layProb; | |
246 | ||
247 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kKaon,mom,iLay+3); | |
10d100d4 | 248 | itsProb[1] *= layProb; |
249 | ||
250 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kPion,mom,iLay+3); | |
251 | itsProb[2] *= layProb; | |
2ca1f4ee | 252 | |
253 | layProb = pars.GetLandauGausNorm(dedx,AliPID::kElectron,mom,iLay+3); | |
254 | itsProb[3] *= layProb; | |
10d100d4 | 255 | } |
256 | ||
257 | // Normalise probabilities | |
258 | Double_t sumProb = 0; | |
259 | for (Int_t iPart = 0; iPart < nPart; iPart++) { | |
260 | sumProb += itsProb[iPart]; | |
261 | } | |
2ca1f4ee | 262 | sumProb += itsProb[2]; // muon cannot be distinguished from pions |
10d100d4 | 263 | |
264 | for (Int_t iPart = 0; iPart < nPart; iPart++) { | |
265 | itsProb[iPart]/=sumProb; | |
266 | } | |
2ca1f4ee | 267 | condprobfun[AliPID::kElectron] = itsProb[3]; |
897a0e31 | 268 | condprobfun[AliPID::kMuon] = itsProb[2]; |
269 | condprobfun[AliPID::kPion] = itsProb[2]; | |
10d100d4 | 270 | condprobfun[AliPID::kKaon] = itsProb[1]; |
271 | condprobfun[AliPID::kProton] = itsProb[0]; | |
272 | return; | |
273 | } | |
15e979c9 | 274 | |
8abeb05b | 275 | //_________________________________________________________________________ |
276 | Int_t AliITSPIDResponse::GetParticleIdFromdEdxVsP(Float_t mom, Float_t signal, Bool_t isSA) const{ | |
277 | // method to get particle identity with simple cuts on dE/dx vs. momentum | |
278 | ||
279 | Double_t massp=AliPID::ParticleMass(AliPID::kProton); | |
280 | Double_t massk=AliPID::ParticleMass(AliPID::kKaon); | |
281 | Double_t bethep=Bethe(mom,massp,isSA); | |
282 | Double_t bethek=Bethe(mom,massk,isSA); | |
283 | if(signal>(0.5*(bethep+bethek))) return AliPID::kProton; | |
284 | Double_t masspi=AliPID::ParticleMass(AliPID::kPion); | |
285 | Double_t bethepi=Bethe(mom,masspi,isSA); | |
286 | if(signal>(0.5*(bethepi+bethek))) return AliPID::kKaon; | |
287 | return AliPID::kPion; | |
288 | ||
289 | } |