Move HMPID QA code to PWG1.
[u/mrichter/AliRoot.git] / HMPID / AliHMPIDPid.cxx
1 /**************************************************************************
2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
3  *                                                                        *
4  * Author: The ALICE Off-line Project.                                    *
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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     delete pPid ; pPid=0x0; return;
50   } 
51   
52   Double_t p[3] = {0}, pmod = 0;
53   if(pTrk->GetOuterHmpPxPyPz(p))  pmod = TMath::Sqrt(p[0]*p[0]+p[1]*p[1]+p[2]*p[2]);  // Momentum of the charged particle
54   
55   else {                                         
56     for(Int_t iPart=0;iPart<nsp;iPart++) prob[iPart]=1.0/(Float_t)nsp;
57     delete pPid ; pPid=0x0; return;
58   } 
59   
60   Double_t hTot=0;                               // Initialize the total height of the amplitude method
61   Double_t *h = new Double_t [nsp];              // number of charged particles to be considered
62
63   Bool_t desert = kTRUE;                                                                                                     //  Flag to evaluate if ThetaC is far ("desert") from the given Gaussians
64   
65   for(Int_t iPart=0;iPart<nsp;iPart++){                                                                                      //  for each particle
66     
67     h[iPart] = 0;                                                                                                            //  reset the height
68     Double_t mass = pPid->ParticleMass(iPart);                                                                             //  with the given mass
69     Double_t cosThetaTh = TMath::Sqrt(mass*mass+pmod*pmod)/(AliHMPIDParam::Instance()->MeanIdxRad()*pmod);                   //  evaluate the theor. Theta Cherenkov
70     if(cosThetaTh>1) continue;                                                                                               //  no light emitted, zero height
71     Double_t thetaCerTh = TMath::ACos(cosThetaTh);                                                                           //  theoretical Theta Cherenkov
72     Double_t sigmaRing = Resolution(thetaCerTh,pTrk);
73     
74     if(sigmaRing==0) {
75       for(Int_t jPart=0;jPart<nsp;jPart++) prob[jPart]=1.0/(Float_t)nsp;
76       delete pPid ; pPid=0x0; return;
77     } 
78     
79     if(TMath::Abs(thetaCerExp-thetaCerTh)<4*sigmaRing) desert = kFALSE;                                                                //   
80     h[iPart] =TMath::Gaus(thetaCerTh,thetaCerExp,sigmaRing,kTRUE);
81     hTot    +=h[iPart]; //total height of all theoretical heights for normalization
82     
83   }//species loop
84
85   for(Int_t iPart=0;iPart<nsp;iPart++) {//species loop to assign probabilities
86     
87     if(!desert) prob[iPart]=h[iPart]/hTot;
88     else prob[iPart]=1.0/(Float_t)nsp;            //all theoretical values are far away from experemental one
89     
90   }
91   
92   delete [] h;
93   delete pPid ; pPid=0x0;
94 }
95 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
96 Double_t AliHMPIDPid::Resolution(Double_t thetaCerTh, AliESDtrack *pTrk)
97 {
98   AliHMPIDParam *pParam = AliHMPIDParam::Instance();
99       
100   AliHMPIDRecon rec;
101   Float_t xRa,yRa,thRa,phRa;
102   pTrk->GetHMPIDtrk(xRa,yRa,thRa,phRa);
103   rec.SetTrack(xRa,yRa,thRa,phRa);
104   Double_t thetaMax = TMath::ACos(1./pParam->MeanIdxRad());
105   Int_t nPhots = (Int_t)(21.*TMath::Sin(thetaCerTh)*TMath::Sin(thetaCerTh)/(TMath::Sin(thetaMax)*TMath::Sin(thetaMax))+0.01);
106
107   Double_t sigmatot = 0;
108   Int_t nTrks = 20;
109   for(Int_t iTrk=0;iTrk<nTrks;iTrk++) {
110     Double_t invSigma = 0;
111     Int_t nPhotsAcc = 0;
112     for(Int_t j=0;j<nPhots;j++){
113       Double_t phi = gRandom->Rndm()*TMath::TwoPi();
114       TVector2 pos; pos=rec.TracePhot(thetaCerTh,phi);
115       if(!pParam->IsInside(pos.X(),pos.Y())) continue;
116       if(pParam->IsInDead(pos.X(),pos.Y())) continue;
117       Double_t sigma2 = pParam->Sigma2(thRa,phRa,thetaCerTh,phi);//photon candidate sigma^2
118       if(sigma2!=0) {
119         invSigma += 1./sigma2;
120         nPhotsAcc++;
121       }
122     }      
123     if(invSigma!=0) sigmatot += 1./TMath::Sqrt(invSigma);  
124   }
125   return sigmatot/nTrks;
126 }