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Tracks momentum value for PID taken from GetOuterHmpPxPyPz()
[u/mrichter/AliRoot.git] / HMPID / AliHMPIDPid.cxx
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3278403b 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
ac66a50d 26#include "AliHMPIDRecon.h" //class header
9eb30f08 27#include <AliESDtrack.h> //FindPid()
ac66a50d 28#include <TRandom.h> //Resolution()
3278403b 29
30//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
31AliHMPIDPid::AliHMPIDPid():TTask("HMPIDrec","HMPIDPid")
32{
33//..
34//init of data members
35//..
36}
37//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
dac53a45 38void AliHMPIDPid::FindPid(AliESDtrack *pTrk,Int_t nsp,Double_t *prob)
3278403b 39{
ac66a50d 40// Calculates probability to be a electron-muon-pion-kaon-proton with the "amplitude" method
3278403b 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
ac66a50d 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
dac53a45 48 for(Int_t iPart=0;iPart<nsp;iPart++) prob[iPart]=1.0/(Float_t)nsp;
9eb30f08 49 return;
50 }
122305ea 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 return;
58 }
59
ac66a50d 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
9eb30f08 62
ac66a50d 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 return;
77 }
78
79 if(TMath::Abs(thetaCerExp-thetaCerTh)<4*sigmaRing) desert = kFALSE; //
80 h[iPart] =TMath::Gaus(thetaCerTh,thetaCerExp,sigmaRing,kTRUE);
9eb30f08 81 hTot +=h[iPart]; //total height of all theoretical heights for normalization
ac66a50d 82
9eb30f08 83 }//species loop
84
dac53a45 85 for(Int_t iPart=0;iPart<nsp;iPart++) {//species loop to assign probabilities
ac66a50d 86
87 if(!desert) prob[iPart]=h[iPart]/hTot;
dac53a45 88 else prob[iPart]=1.0/(Float_t)nsp; //all theoretical values are far away from experemental one
ac66a50d 89
9eb30f08 90 }
ac66a50d 91
dac53a45 92 delete [] h;
ac66a50d 93 delete pPid ; pPid=0x0;
3278403b 94}
95//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
ac66a50d 96Double_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}