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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 | // AliHMPIDPid // | |
19 | // // | |
20 | // HMPID class to perfom particle identification // | |
21 | // // | |
22 | ////////////////////////////////////////////////////////////////////////// | |
23 | ||
24 | #include "AliHMPIDPid.h" //class header | |
25 | #include "AliHMPIDParam.h" //class header | |
26 | #include "AliHMPIDRecon.h" //class header | |
27 | #include <AliESDtrack.h> //FindPid() | |
28 | #include <TRandom.h> //Resolution() | |
29 | ||
30 | //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ | |
31 | AliHMPIDPid::AliHMPIDPid():TTask("HMPIDrec","HMPIDPid") | |
32 | { | |
33 | //.. | |
34 | //init of data members | |
35 | //.. | |
36 | } | |
37 | //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ | |
38 | void AliHMPIDPid::FindPid(AliESDtrack *pTrk,Int_t nsp,Double_t *prob) | |
39 | { | |
40 | // Calculates probability to be a electron-muon-pion-kaon-proton with the "amplitude" method | |
41 | // from the given Cerenkov angle and momentum assuming no initial particle composition | |
42 | // (i.e. apriory probability to be the particle of the given sort is the same for all sorts) | |
43 | ||
44 | AliPID *pPid = new AliPID(); | |
45 | Double_t thetaCerExp = pTrk->GetHMPIDsignal(); // measured thetaCherenkov | |
46 | ||
47 | if(thetaCerExp<=0){ //HMPID does not find anything reasonable for this track, assign 0.2 for all species | |
48 | for(Int_t iPart=0;iPart<nsp;iPart++) prob[iPart]=1.0/(Float_t)nsp; | |
49 | return; | |
50 | } | |
51 | ||
52 | Double_t pmod = pTrk->GetP(); // Momentum of the charged particle | |
53 | Double_t hTot=0; // Initialize the total height of the amplitude method | |
54 | Double_t *h = new Double_t [nsp]; // number of charged particles to be considered | |
55 | ||
56 | Bool_t desert = kTRUE; // Flag to evaluate if ThetaC is far ("desert") from the given Gaussians | |
57 | ||
58 | for(Int_t iPart=0;iPart<nsp;iPart++){ // for each particle | |
59 | ||
60 | h[iPart] = 0; // reset the height | |
61 | Double_t mass = pPid->ParticleMass(iPart); // with the given mass | |
62 | Double_t cosThetaTh = TMath::Sqrt(mass*mass+pmod*pmod)/(AliHMPIDParam::Instance()->MeanIdxRad()*pmod); // evaluate the theor. Theta Cherenkov | |
63 | if(cosThetaTh>1) continue; // no light emitted, zero height | |
64 | Double_t thetaCerTh = TMath::ACos(cosThetaTh); // theoretical Theta Cherenkov | |
65 | Double_t sigmaRing = Resolution(thetaCerTh,pTrk); | |
66 | ||
67 | if(sigmaRing==0) { | |
68 | for(Int_t jPart=0;jPart<nsp;jPart++) prob[jPart]=1.0/(Float_t)nsp; | |
69 | return; | |
70 | } | |
71 | ||
72 | if(TMath::Abs(thetaCerExp-thetaCerTh)<4*sigmaRing) desert = kFALSE; // | |
73 | h[iPart] =TMath::Gaus(thetaCerTh,thetaCerExp,sigmaRing,kTRUE); | |
74 | hTot +=h[iPart]; //total height of all theoretical heights for normalization | |
75 | ||
76 | }//species loop | |
77 | ||
78 | for(Int_t iPart=0;iPart<nsp;iPart++) {//species loop to assign probabilities | |
79 | ||
80 | if(!desert) prob[iPart]=h[iPart]/hTot; | |
81 | else prob[iPart]=1.0/(Float_t)nsp; //all theoretical values are far away from experemental one | |
82 | ||
83 | } | |
84 | ||
85 | delete [] h; | |
86 | delete pPid ; pPid=0x0; | |
87 | } | |
88 | //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ | |
89 | Double_t AliHMPIDPid::Resolution(Double_t thetaCerTh, AliESDtrack *pTrk) | |
90 | { | |
91 | AliHMPIDParam *pParam = AliHMPIDParam::Instance(); | |
92 | ||
93 | AliHMPIDRecon rec; | |
94 | Float_t xRa,yRa,thRa,phRa; | |
95 | pTrk->GetHMPIDtrk(xRa,yRa,thRa,phRa); | |
96 | rec.SetTrack(xRa,yRa,thRa,phRa); | |
97 | Double_t thetaMax = TMath::ACos(1./pParam->MeanIdxRad()); | |
98 | Int_t nPhots = (Int_t)(21.*TMath::Sin(thetaCerTh)*TMath::Sin(thetaCerTh)/(TMath::Sin(thetaMax)*TMath::Sin(thetaMax))+0.01); | |
99 | ||
100 | Double_t sigmatot = 0; | |
101 | Int_t nTrks = 20; | |
102 | for(Int_t iTrk=0;iTrk<nTrks;iTrk++) { | |
103 | Double_t invSigma = 0; | |
104 | Int_t nPhotsAcc = 0; | |
105 | for(Int_t j=0;j<nPhots;j++){ | |
106 | Double_t phi = gRandom->Rndm()*TMath::TwoPi(); | |
107 | TVector2 pos; pos=rec.TracePhot(thetaCerTh,phi); | |
108 | if(!pParam->IsInside(pos.X(),pos.Y())) continue; | |
109 | if(pParam->IsInDead(pos.X(),pos.Y())) continue; | |
110 | Double_t sigma2 = pParam->Sigma2(thRa,phRa,thetaCerTh,phi);//photon candidate sigma^2 | |
111 | if(sigma2!=0) { | |
112 | invSigma += 1./sigma2; | |
113 | nPhotsAcc++; | |
114 | } | |
115 | } | |
116 | if(invSigma!=0) sigmatot += 1./TMath::Sqrt(invSigma); | |
117 | } | |
118 | return sigmatot/nTrks; | |
119 | } |