* provided "as is" without express or implied warranty. *
**************************************************************************/
-//-----------------------------------------------------------------
-// Implementation of the TRD PID class
-// Assigns the electron and pion liklihoods for each ESD track.
-// The function MakePID(AliESD *event) calculates the probability
-// of having dedx and the probability of having timbin at a given
-// momentum (mom) and particle type k (0 for e) and (2 for pi)
-// from the precalculated timbin distributions.
-// Prashant Shukla <shukla@pi0.physi.uni-heidelberg.de>
-//-----------------------------------------------------------------
+/* $Id$ */
-#include "AliTRDpidESD.h"
+////////////////////////////////////////////////////////////////////////////
+// //
+// Implementation of the TRD PID class //
+// //
+// Assigns the electron and pion likelihoods to each ESD track. //
+// The function MakePID(AliESD *event) calculates the probability //
+// of having dedx and a maximum timbin at a given //
+// momentum (mom) and particle type k //
+// from the precalculated distributions. //
+// //
+// Authors : //
+// Prashant Shukla <shukla@pi0.physi.uni-heidelberg.de> (Original version)//
+// Alex Bercuci (a.bercuci@gsi.de) //
+// //
+////////////////////////////////////////////////////////////////////////////
+
+#include "AliLog.h"
#include "AliESD.h"
#include "AliESDtrack.h"
+
+#include "AliTRDpidESD.h"
+#include "AliTRDgeometry.h"
#include "AliTRDcalibDB.h"
-#include "AliTRDCalPIDLQ.h"
+#include "AliRun.h"
+#include "AliTRDtrack.h"
+#include "Cal/AliTRDCalPIDLQ.h"
ClassImp(AliTRDpidESD)
-//_________________________________________________________________________
-AliTRDpidESD::AliTRDpidESD(Double_t *param)
+ Bool_t AliTRDpidESD::fCheckTrackStatus = kTRUE;
+ Bool_t AliTRDpidESD::fCheckKinkStatus = kFALSE;
+ Int_t AliTRDpidESD::fMinPlane = 0;
+
+//_____________________________________________________________________________
+AliTRDpidESD::AliTRDpidESD()
+ :TObject()
{
//
- // The main constructor
+ // Default constructor
//
- fMIP=param[0]; // MIP signal
- fRes=param[1]; // relative resolution
- fRange=param[2]; // PID "range" (in sigmas)
+
}
-Double_t AliTRDpidESD::Bethe(Double_t bg)
+//_____________________________________________________________________________
+AliTRDpidESD::AliTRDpidESD(const AliTRDpidESD &p)
+ :TObject(p)
{
//
- // Parametrization of the Bethe-Bloch-curve
- // The parametrization is the same as for the TPC and is taken from Lehrhaus.
+ // AliTRDpidESD copy constructor
//
- // This parameters have been adjusted to averaged values from GEANT
- const Double_t kP1 = 7.17960e-02;
- const Double_t kP2 = 8.54196;
- const Double_t kP3 = 1.38065e-06;
- const Double_t kP4 = 5.30972;
- const Double_t kP5 = 2.83798;
-
- // This parameters have been adjusted to Xe-data found in:
- // Allison & Cobb, Ann. Rev. Nucl. Sci. (1980), 30, 253
- //const Double_t kP1 = 0.76176E-1;
- //const Double_t kP2 = 10.632;
- //const Double_t kP3 = 3.17983E-6;
- //const Double_t kP4 = 1.8631;
- //const Double_t kP5 = 1.9479;
-
- // Lower cutoff of the Bethe-Bloch-curve to limit step sizes
- const Double_t kBgMin = 0.8;
- const Double_t kBBMax = 6.83298;
- //const Double_t kBgMin = 0.6;
- //const Double_t kBBMax = 17.2809;
- //const Double_t kBgMin = 0.4;
- //const Double_t kBBMax = 82.0;
-
- if (bg > kBgMin) {
- Double_t yy = bg / TMath::Sqrt(1. + bg*bg);
- Double_t aa = TMath::Power(yy,kP4);
- Double_t bb = TMath::Power((1./bg),kP5);
- bb = TMath::Log(kP3 + bb);
- return ((kP2 - aa - bb)*kP1 / aa);
- }
- else {
- return kBBMax;
- }
+ ((AliTRDpidESD &) p).Copy(*this);
}
-//_________________________________________________________________________
+//_____________________________________________________________________________
+AliTRDpidESD &AliTRDpidESD::operator=(const AliTRDpidESD &p)
+{
+ //
+ // Assignment operator
+ //
+
+ if (this != &p) ((AliTRDpidESD &) p).Copy(*this);
+ return *this;
+
+}
+
+//_____________________________________________________________________________
+void AliTRDpidESD::Copy(TObject &p) const
+{
+ //
+ // Copy function
+ //
+
+ ((AliTRDpidESD &) p).fCheckTrackStatus = fCheckTrackStatus;
+ ((AliTRDpidESD &) p).fCheckKinkStatus = fCheckKinkStatus;
+ ((AliTRDpidESD &) p).fMinPlane = fMinPlane;
+
+}
+
+//_____________________________________________________________________________
Int_t AliTRDpidESD::MakePID(AliESD *event)
{
//
- // This function calculates the "detector response" PID probabilities
+ // This function calculates the PID probabilities based on TRD signals
+ //
+ // The method produces probabilities based on the charge
+ // and the position of the maximum time bin in each layer.
+ // The dE/dx information can be used as global charge or 2 to 3
+ // slices. Check AliTRDCalPIDLQ and AliTRDCalPIDLQRef for the actual
+ // implementation.
+ //
+ // Author
+ // Alex Bercuci (A.Bercuci@gsi.de) 2nd May 2007
+
+ AliTRDcalibDB *calibration = AliTRDcalibDB::Instance();
+ if (!calibration) {
+ AliErrorGeneral("AliTRDpidESD::MakePID()"
+ ,"No access to calibration data");
+ return -1;
+ }
+
+ // Retrieve the CDB container class with the probability distributions
+ const AliTRDCalPIDLQ *pd = calibration->GetPIDLQObject();
+ if (!pd) {
+ AliErrorGeneral("AliTRDpidESD::MakePID()"
+ ,"No access to AliTRDCalPIDLQ");
+ return -1;
+ }
+
+
+ // Loop through all ESD tracks
+ Double_t p[10];
+ AliESDtrack *t = 0x0;
+ Double_t dedx[AliTRDtrack::kNslice], dEdx;
+ Int_t timebin;
+ Float_t mom, length, probTotal;
+ Int_t nPlanePID;
+ for (Int_t i=0; i<event->GetNumberOfTracks(); i++) {
+ t = event->GetTrack(i);
+
+ // Check track
+ if(!CheckTrack(t)) continue;
+
+ // Skip tracks which have no TRD signal at all
+ if (t->GetTRDsignal() == 0.) continue;
+
+ // Loop over detector layers
+ mom = 0.; //t->GetP();
+ length = 0.;
+ probTotal = 0.;
+ nPlanePID = 0;
+ for (Int_t iSpecies = 0; iSpecies < AliPID::kSPECIES; iSpecies++) p[iSpecies] = 1.;
+ for (Int_t iPlan = 0; iPlan < AliTRDgeometry::kNplan; iPlan++) {
+ // read data for track segment
+ for(int iSlice=0; iSlice<AliTRDtrack::kNslice; iSlice++)
+ dedx[iSlice] = t->GetTRDsignals(iPlan, iSlice);
+ dEdx = t->GetTRDsignals(iPlan, -1);
+ timebin = t->GetTRDTimBin(iPlan);
+
+ // check data
+ if ((dEdx <= 0.) || (timebin <= -1.)) continue;
+
+ // retrive kinematic info for this track segment
+ if(!GetTrackSegmentKine(t, iPlan, mom, length)) continue;
+
+ // this track segment has fulfilled all requierments
+ nPlanePID++;
+
+ // Get the probabilities for the different particle species
+ for (Int_t iSpecies = 0; iSpecies < AliPID::kSPECIES; iSpecies++) {
+ p[iSpecies] *= pd->GetProbability(iSpecies, mom, dedx, length);
+ p[iSpecies] *= pd->GetProbabilityT(iSpecies, mom, timebin);
+ probTotal += p[iSpecies];
+ }
+ }
+
+ // normalize probabilities
+ if(probTotal > 0.)
+ for (Int_t iSpecies = 0; iSpecies < AliPID::kSPECIES; iSpecies++)
+ if(nPlanePID > fMinPlane) p[iSpecies] /= probTotal;
+ else p[iSpecies] = 1.0;
+
+
+ // book PID to the track
+ t->SetTRDpid(p);
+ }
+
+ return 0;
+}
+
+//_____________________________________________________________________________
+Bool_t AliTRDpidESD::CheckTrack(AliESDtrack *t)
+{
+ //
+ // Check if track is eligible for PID calculations
//
-
- AliTRDcalibDB* calibration = AliTRDcalibDB::Instance();
- if (!calibration)
- return -1;
-
- // The class AliTRDCalPIDLQ contains precalculated prob dis.
- AliTRDCalPIDLQ *pd = calibration->GetPIDLQObject();
-
- // Example to get mean for particle 2 (pi) and momentum number 4 (2 GeV)
- // printf("%.2f \n", pd->GetMean(2, 4));
- // Example of use of Copy Constructor
- // AliTRDCalPIDLQ *pd1 = new AliTRDCalPIDLQ(*pd);
-
- Int_t ntrk=event->GetNumberOfTracks();
- for (Int_t i=0; i<ntrk; i++) {
- AliESDtrack *t=event->GetTrack(i);
- if ((t->GetStatus()&AliESDtrack::kTRDin)==0)
- if ((t->GetStatus()&AliESDtrack::kTRDout)==0)
- if ((t->GetStatus()&AliESDtrack::kTRDrefit)==0) continue;
- if(t->GetTRDsignal()==0) continue;
- // Int_t ns=AliESDtrack::kSPECIES;
- Int_t ns=AliPID::kSPECIES;
- Double_t p[10];
- Double_t mom=t->GetP();
- Double_t probTotal=0.0;
- for (Int_t j=0; j<ns; j++) {
- p[j]=1.;
- for (Int_t ilayer=0; ilayer <6; ilayer++) {
- Double_t dedx=t->GetTRDsignals(ilayer);
- Int_t timbin=t->GetTRDTimBin(ilayer);
- p[j]*= pd->GetProbability(j,mom,dedx);
- p[j]*= pd->GetProbabilityT(j,mom,timbin);
- p[j]*= 100;
- } // loop over layers
- probTotal+=p[j];
- } //loop over particle species
- // printf(" %f %d %f %f %f \n", mom, timbin, p[0], p[1], p[2]);
- for (Int_t j=0; j<ns; j++) {
- if(probTotal) p[j]/= probTotal;
- else p[j]=1.0;
- // p[j]=1.;
- } //loop over particle species
- t->SetTRDpid(p);
- } //loop over tracks
- delete pd;
- return 0;
+
+ // Check the ESD track status
+ if (fCheckTrackStatus) {
+ if (((t->GetStatus() & AliESDtrack::kTRDout ) == 0) &&
+ ((t->GetStatus() & AliESDtrack::kTRDrefit) == 0)) return kFALSE;
+ }
+
+ // Check for ESD kink tracks
+ if (fCheckKinkStatus && (t->GetKinkIndex(0) != 0)) return kFALSE;
+
+ return kTRUE;
}
+
+//_____________________________________________________________________________
+Bool_t AliTRDpidESD::GetTrackSegmentKine(AliESDtrack *t, Int_t plan, Float_t &mom, Float_t &length)
+{
+ //
+ // Retrive momentum "mom" and track "length" in TRD chamber from plane
+ // "plan" according to information stored in AliESDtrack "t".
+ //
+
+ if(!gAlice){
+ AliErrorGeneral("AliTRDpidESD::GetTrackSegmentKine()"
+ ,"No gAlice object to retrive TRDgeometry and Magnetic fied - this has to be removed in the future.");
+ return kFALSE;
+ }
+
+ // Retrieve TRD geometry -> Maybe there is a better way to do this
+ AliTRDgeometry trdGeom;
+ const Float_t kAmHalfWidth = AliTRDgeometry::AmThick() / 2.;
+ const Float_t kDrWidth = AliTRDgeometry::DrThick();
+
+
+ // retrive the magnetic field
+ Double_t xyz0[3] = { 0., 0., 0.}, xyz1[3];
+ Double_t b[3], alpha;
+ gAlice->Field(xyz0,b); // b[] is in kilo Gauss
+ Float_t field = b[2] * 0.1; // Tesla
+
+ // find momentum at chamber entrance and track length in chamber
+ AliExternalTrackParam *param = (plan<3) ? new AliExternalTrackParam(*t->GetInnerParam()) : new AliExternalTrackParam(*t->GetOuterParam());
+
+ param->PropagateTo(trdGeom.GetTime0(plan)+kAmHalfWidth, field);
+ param->GetXYZ(xyz0);
+ alpha = param->GetAlpha();
+ param->PropagateTo(trdGeom.GetTime0(plan)-kAmHalfWidth-kDrWidth, field);
+ // eliminate track segments which are crossing SM boundaries along chamber
+ if(TMath::Abs(alpha-param->GetAlpha())>.01){
+ delete param;
+ return kFALSE;
+ }
+ param->GetXYZ(xyz1);
+ length = sqrt(
+ (xyz1[0]-xyz0[0])*(xyz1[0]-xyz0[0])+
+ (xyz1[1]-xyz0[1])*(xyz1[1]-xyz0[1])+
+ (xyz1[2]-xyz0[2])*(xyz1[2]-xyz0[2])
+ );
+ param->GetPxPyPz(xyz1);
+ mom = sqrt(xyz1[0]*xyz1[0] + xyz1[1]*xyz1[1] + xyz1[2]*xyz1[2]);
+ delete param;
+
+ return kTRUE;
+}
+
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