Fix for report #72089 changes to AliTOFPIDResponse to be commited in STEER (Roberto)
[u/mrichter/AliRoot.git] / STEER / AliTOFPIDResponse.cxx
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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 "AliTOFPIDResponse.h"
27
28 ClassImp(AliTOFPIDResponse)
29
30 //_________________________________________________________________________
31 AliTOFPIDResponse::AliTOFPIDResponse(): 
32   fSigma(0),
33   fPmax(0),         // zero at 0.5 GeV/c for pp
34   fTime0(0)
35 {
36   // Reset T0 info
37   ResetT0info();
38   SetMomBoundary();
39 }
40 //_________________________________________________________________________
41 AliTOFPIDResponse::AliTOFPIDResponse(Double_t *param):
42   fSigma(param[0]),
43   fPmax(0),          // zero at 0.5 GeV/c for pp
44   fTime0(0)
45 {
46   //
47   //  The main constructor
48   //
49   //
50
51   //fPmax=TMath::Exp(-0.5*3*3)/fSigma; // ~3 sigma at 0.5 GeV/c for PbPb 
52
53   // Reset T0 info
54   ResetT0info();
55   SetMomBoundary();
56 }
57 //_________________________________________________________________________
58 Double_t 
59 AliTOFPIDResponse::GetMismatchProbability(Double_t p, Double_t mass) const {
60   //
61   // Returns the probability of mismatching 
62   // assuming 1/(p*beta)^2 scaling
63   //
64   const Double_t km=0.5;                   // "reference" momentum (GeV/c)
65
66   Double_t ref2=km*km*km*km/(km*km + mass*mass);// "reference" (p*beta)^2
67   Double_t p2beta2=p*p*p*p/(p*p + mass*mass);
68
69   return fPmax*ref2/p2beta2;
70 }
71 //_________________________________________________________________________
72 Double_t AliTOFPIDResponse::GetExpectedSigma(Float_t mom, Float_t time, Float_t mass) const {
73   //
74   // Return the expected sigma of the PID signal for the specified
75   // particle type.
76   // If the operation is not possible, return a negative value.
77   //
78
79   Double_t dpp=0.018*mass/mom;      //mean relative pt resolution;
80
81  
82   Double_t sigma = dpp*time/(1.+ mom*mom/(mass*mass));
83   
84   Int_t index = GetMomBin(mom);
85
86   Double_t t0res = fT0resolution[index];
87
88   return TMath::Sqrt(sigma*sigma + 50.0*50.0/mom/mom + fSigma*fSigma + t0res*t0res);
89
90 }
91 //_________________________________________________________________________
92 Int_t AliTOFPIDResponse::GetMomBin(Float_t p) const{
93   Int_t i=0;
94   while(p > fPCutMin[i] && i < fNmomBins) i++;
95   if(i > 0) i--;
96
97   return i;
98 }
99 //_________________________________________________________________________
100 void AliTOFPIDResponse::SetMomBoundary(){
101   fPCutMin[0] = 0.3;
102   fPCutMin[1] = 0.5;
103   fPCutMin[2] = 0.6;
104   fPCutMin[3] = 0.7;
105   fPCutMin[4] = 0.8;
106   fPCutMin[5] = 0.9;
107   fPCutMin[6] = 1;
108   fPCutMin[7] = 1.2;
109   fPCutMin[8] = 1.5;
110   fPCutMin[9] = 2;
111   fPCutMin[10] = 3;  
112 }