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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 | // Implementation of the ITS PID class | |
18 | // Very naive one... Should be made better by the detector experts... | |
19 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch | |
20 | //----------------------------------------------------------------- | |
21 | ||
22 | #include "AliITSpidESD.h" | |
23 | #include "AliESD.h" | |
24 | #include "AliESDtrack.h" | |
25 | ||
26 | ClassImp(AliITSpidESD) | |
27 | ||
28 | //_________________________________________________________________________ | |
29 | AliITSpidESD::AliITSpidESD(Double_t *param) | |
30 | { | |
31 | // | |
32 | // The main constructor | |
33 | // | |
34 | fMIP=param[0]; | |
35 | fRes=param[1]; | |
36 | fRange=param[2]; | |
37 | } | |
38 | ||
39 | Double_t AliITSpidESD::Bethe(Double_t bg) { | |
40 | // | |
41 | // This is the Bethe-Bloch function normalised to 1 at the minimum | |
42 | // | |
43 | Double_t bg2=bg*bg; | |
44 | Double_t bethe; | |
45 | /*if (bg<3.5) | |
46 | bethe=(1.+ bg2)/bg2*(log(5940*bg2) - bg2/(1.+ bg2)); | |
47 | else*/ // not 100% clear why... | |
48 | bethe=(1.+ bg2)/bg2*(log(3.5*5940*bg) - bg2/(1.+ bg2)); | |
49 | return bethe/11.091; | |
50 | } | |
51 | ||
52 | //_________________________________________________________________________ | |
53 | Int_t AliITSpidESD::MakePID(AliESD *event) | |
54 | { | |
55 | // | |
56 | // This function calculates the "detector response" PID probabilities | |
57 | // | |
58 | static const Double_t masses[]={ | |
59 | 0.000511, 0.105658, 0.139570, 0.493677, 0.938272, 1.875613 | |
60 | }; | |
61 | Int_t ntrk=event->GetNumberOfTracks(); | |
62 | for (Int_t i=0; i<ntrk; i++) { | |
63 | AliESDtrack *t=event->GetTrack(i); | |
64 | if ((t->GetStatus()&AliESDtrack::kITSin )==0) | |
65 | if ((t->GetStatus()&AliESDtrack::kITSout)==0) continue; | |
66 | Double_t mom=t->GetP(); | |
67 | Double_t dedx=t->GetITSsignal()/fMIP; | |
68 | Int_t ns=AliESDtrack::kSPECIES; | |
69 | Double_t p[10]; | |
70 | for (Int_t j=0; j<ns; j++) { | |
71 | Double_t mass=masses[j]; | |
72 | Double_t bethe=Bethe(mom/mass); | |
73 | Double_t sigma=fRes*bethe; | |
74 | if (TMath::Abs(dedx-bethe) > fRange*sigma) { | |
75 | p[j]=TMath::Exp(-0.5*fRange*fRange)/sigma; | |
76 | continue; | |
77 | } | |
78 | p[j]=TMath::Exp(-0.5*(dedx-bethe)*(dedx-bethe)/(sigma*sigma))/sigma; | |
79 | } | |
80 | t->SetITSpid(p); | |
81 | } | |
82 | return 0; | |
83 | } |