1 //========================================================================
2 // Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved.
4 // Author: The ALICE Off-line Project.
5 // Contributors are mentioned in the code where appropriate.
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 //========================================================================
16 // Class AliEMCALTrack
17 // ---------------------
18 // A class implementing a track which is propagated to EMCAL and
19 // matches and EMCAL cluster.
20 // This track object will not update Kalman parameters, but it
21 // allows for track propagation and suitable energy loss correction,
22 // even in an environment with a variable magnetic field, which is not
23 // well managed in the AliExternalTrackParam class.
24 // ------------------------------------------------------------------------
25 // author: A. Pulvirenti (alberto.pulvirenti@ct.infn.it)
26 //=========================================================================
28 #include "Riostream.h"
33 #include "AliESDtrack.h"
35 #include "AliEMCALTrack.h"
37 Bool_t AliEMCALTrack::fgUseOuterParams = kTRUE;
38 Bool_t AliEMCALTrack::fgCorrectForEL = kFALSE;
39 Bool_t AliEMCALTrack::fgSortByPt = kTRUE;
41 ClassImp(AliEMCALTrack)
43 //------------------------------------------------------------------------------
45 AliEMCALTrack::AliEMCALTrack()
46 : AliExternalTrackParam(),
48 fClusterDist(1000.0), // default: extremely large distance
49 fMass(0.13957018), // default: pion mass
54 // Default constructor.
55 // Sets to meaningless values the indexes corresponding to
56 // ESD seed track and matched cluster.
61 //------------------------------------------------------------------------------
63 AliEMCALTrack::AliEMCALTrack(const AliESDtrack& t)
64 : AliExternalTrackParam(),
69 fSeedLabel(t.GetLabel())
72 // Constructor from AliESDtrack
75 // parameters are chosen according to static variable fUseOuterParams
76 Double_t alpha=0., x=0., params[5], cov[15];
77 if (fgUseOuterParams) {
78 if(t.GetOuterParam()){
79 t.GetOuterExternalParameters(alpha, x, params);
80 t.GetOuterExternalCovariance(cov);
82 else{ // no outer param available leave the default as is
88 t.GetExternalParameters(x, params);
89 t.GetExternalCovariance(cov);
92 if (alpha < -TMath::Pi()) alpha += TMath::TwoPi();
93 else if (alpha >= TMath::Pi()) alpha -= TMath::TwoPi();
95 // set this accordingly
96 Set(x, alpha, params, cov);
99 //------------------------------------------------------------------------------
101 AliEMCALTrack::AliEMCALTrack(const AliEMCALTrack& t)
102 : AliExternalTrackParam(t),
103 fClusterIndex(t.fClusterIndex),
104 fClusterDist(t.fClusterDist),
106 fSeedIndex(t.fSeedIndex),
107 fSeedLabel(t.fSeedLabel)
114 //------------------------------------------------------------------------------
116 AliEMCALTrack& AliEMCALTrack::operator=(const AliEMCALTrack &t)
119 // Assignment operator
120 // Works like copy constructor
123 fClusterIndex = t.fClusterIndex;
124 fClusterDist = t.fClusterDist;
128 fSeedIndex = t.fSeedIndex;
129 fSeedLabel = t.fSeedLabel;
133 //------------------------------------------------------------------------------
135 Int_t AliEMCALTrack::Compare(const TObject *obj) const
139 // How tracks are compared depends on the static flag
140 // "fSortByPt" (boolean):
141 // true => tracks are compared w.r. to their transverse momentum
142 // false => tracks are compared w.r. to their distance from cluster
145 AliEMCALTrack *that = (AliEMCALTrack*)obj;
147 Double_t thisP[3], thisVal=0., thatP[3], thatVal=0.;
150 this->GetPxPyPz(thisP);
151 that->GetPxPyPz(thatP);
152 thisVal = TMath::Sqrt(thisP[0]*thisP[0] + thisP[1]*thisP[1]);
153 thatVal = TMath::Sqrt(thatP[0]*thatP[0] + thatP[1]*thatP[1]);
156 thisVal = this->GetClusterDist();
157 thatVal = that->GetClusterDist();
160 if (thisVal > thatVal) return 1;
161 else if (thisVal < thatVal) return -1;
165 //------------------------------------------------------------------------------
167 Bool_t AliEMCALTrack::PropagateTo(Double_t xk, Double_t d, Double_t x0)
170 // Propagates a track to the plane defined by x='xk'.
171 // Second parameter is the width (in units of rad. length) crossed by the track.
172 // Third parameter is the reference radiation length used.
173 // Track propagation includes computing energy loss (modifies curvature)
174 // and multiple scattering perturbation (alters covariance matrix), if requested.
175 // Method returns kFALSE when something goes wrong with computations.
177 // An additional operation (thanks to Yuri Belikov) is done to check
178 // when the track crosses a sector boundary. If this happens,
179 // the local track reference frame is adjusted accordingly.
183 Double_t field = GetBz();
184 Double_t width = TMath::Pi() / 9.0; // width of TPC/TRD/EMCAL sector (= 20 deg)
185 Double_t ymax = TMath::Abs(xk * TMath::Tan(0.5 * width)); // max allowed Y in local coords at distance xk
187 // first check: try to compute the local 'y' at the distance 'xk':
188 // if this attempt fails, the propagation cannot be done
189 if (!GetYAt(xk, field, y)) return kFALSE;
191 // if is -ymax < y < ymax ==> 'direct' propagation is done;
192 if (TMath::Abs(y) <= ymax) return SimplePropagation(xk, d, x0);
194 // otherwise, try change a sector to find one where the propagation is ok
195 Int_t i=0, incr=0, istart=0, nloops=0;
196 Double_t alpha = GetAlpha();
197 incr = (y > ymax) ? 1 : -1;
198 if (alpha < 0.0) alpha += TMath::TwoPi();
199 istart = (Int_t)(alpha / width);
200 for (i = istart, nloops = 0; nloops < 18; i += incr, nloops++) {
203 alpha = ((Double_t)i + 0.5) * width;
205 if (GetYAt(xk, field, y)) {
206 if (TMath::Abs(y) <= ymax) {
207 AliDebug(1,Form("Required change from sector %d to sector %d to succeed in propagation", istart, i));
208 return SimplePropagation(xk, d, x0);
214 // if the routine exits from the loop and reaches this point,
215 // it means that none of the rotations succeeded
216 AliWarning("Track propagation fails in every sector. Impossible to propagate.");
220 //------------------------------------------------------------------------------
222 Double_t AliEMCALTrack::StraightPropagateTo(Double_t xk, Double_t &x, Double_t &y, Double_t &z)
225 // Does propagation with a straight line approximation.
226 // This operation does not update track parameters, but it returns a point
227 // in space, according to this propagation, which is stored in
228 // the arguments #2, #3 and #4
231 Double_t oldX = GetX(), oldY = GetY(), oldZ = GetZ();
235 newPos[1] = oldY * xk / oldX;
236 newPos[2] = oldZ * xk / oldX;
238 Double_t cs = TMath::Cos(GetAlpha()), sn = TMath::Sin(GetAlpha());
239 x = newPos[0]*cs - newPos[1]*sn;
240 y = newPos[0]*sn + newPos[1]*cs;
246 //------------------------------------------------------------------------------
248 Bool_t AliEMCALTrack::PropagateToGlobal(Double_t x, Double_t y, Double_t z, Double_t d, Double_t x0)
251 // Propagate to a point specified with its global XYZ coordinates.
252 // Here, the correct value of the 'X' parameter to be sent to "PropagateTo" is computed.
255 TVector3 vc(x, y, z);
256 Double_t width = 20.0; // width of TPC/TRD/EMCAL sector
257 Double_t phi = vc.Phi() * TMath::RadToDeg();
258 if (phi < 0.0) phi += 360.0;
260 Int_t isector = (Int_t)(phi / width);
261 Double_t rotation = ((Double_t)isector + 0.5) * width;
262 vc.RotateZ(-rotation * TMath::DegToRad());
264 return PropagateTo(vc.X(), d, x0);
267 //------------------------------------------------------------------------------
269 Bool_t AliEMCALTrack::SimplePropagation(Double_t xk, Double_t d, Double_t x0)
272 // Recall base class method for track propagation.
280 if (!AliExternalTrackParam::PropagateToBxByBz(xk, field)) return kFALSE;
282 // EL correction is computed only if requested...
283 if (!fgCorrectForEL) return kTRUE;
284 return AliExternalTrackParam::CorrectForMeanMaterial(d, x0, GetMass());