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4 * Author: The ALICE Off-line Project. *
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14 **************************************************************************/
16 //-----------------------------------------------------------------
17 // Implementation of the TPC PID class
18 // Very naive one... Should be made better by the detector experts...
19 // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch
20 //-----------------------------------------------------------------
22 #include "AliTPCpidESD.h"
23 #include "AliESDEvent.h"
24 #include "AliESDtrack.h"
26 ClassImp(AliTPCpidESD)
28 //_________________________________________________________________________
29 AliTPCpidESD::AliTPCpidESD(Double_t *param):
35 // The main constructor
42 Double_t AliTPCpidESD::Bethe(Double_t bg) {
44 // This is the Bethe-Bloch function normalised to 1 at the minimum
47 Double_t beta2 = bg2/(1.+ bg2);
49 return 8.62702e-2*(9.14550 - beta2 - TMath::Log(3.51000e-5 + 1./bg2))/beta2;
52 //_________________________________________________________________________
53 Int_t AliTPCpidESD::MakePID(AliESDEvent *event)
56 // This function calculates the "detector response" PID probabilities
58 Int_t ntrk=event->GetNumberOfTracks();
59 for (Int_t i=0; i<ntrk; i++) {
60 AliESDtrack *t=event->GetTrack(i);
61 if ((t->GetStatus()&AliESDtrack::kTPCin )==0)
62 if ((t->GetStatus()&AliESDtrack::kTPCout)==0) continue;
64 Double_t mom=t->GetP();
65 const AliExternalTrackParam *in=t->GetInnerParam();
66 if (in) mom=in->GetP();
67 Double_t dedx=t->GetTPCsignal()/fMIP;
68 Bool_t mismatch=kTRUE, heavy=kTRUE;
69 for (Int_t j=0; j<AliPID::kSPECIES; j++) {
70 Double_t mass=AliPID::ParticleMass(j);
71 Double_t bethe=Bethe(mom/mass);
72 Double_t sigma=fRes*bethe;
73 if (TMath::Abs(dedx-bethe) > fRange*sigma) {
74 p[j]=TMath::Exp(-0.5*fRange*fRange)/sigma;
76 p[j]=TMath::Exp(-0.5*(dedx-bethe)*(dedx-bethe)/(sigma*sigma))/sigma;
80 // Check for particles heavier than (AliPID::kSPECIES - 1)
81 if (dedx < (bethe + fRange*sigma)) heavy=kFALSE;
86 for (Int_t j=0; j<AliPID::kSPECIES; j++) p[j]=1/AliPID::kSPECIES;
90 if (heavy) t->ResetStatus(AliESDtrack::kTPCpid);