[u/mrichter/AliRoot.git] / STEER / AliTrackFitterStraight.cxx

#include "TMatrixDSym.h"
#include "TMatrixD.h"
#include "AliTrackFitterStraight.h"

ClassImp(AliTrackFitterStraight)

AliTrackFitterStraight::AliTrackFitterStraight():
  AliTrackFitter()
{
  //
  // default constructor
  //
  fAlpha = 0.;
  for (Int_t i=0;i<5;i++) fSumXY[i] = 0;
  fSumYY = 0;
  for (Int_t i=0;i<5;i++) fSumXZ[i] = 0;
  fSumZZ = 0;
  fNUsed = 0;
  fConv = kFALSE;
}


AliTrackFitterStraight::AliTrackFitterStraight(AliTrackPointArray *array, Bool_t owner):
  AliTrackFitter(array,owner)
{
  //
  // Constructor
  //
  fAlpha = 0.;
  for (Int_t i=0;i<5;i++) fSumXY[i] = 0;
  fSumYY = 0;
  for (Int_t i=0;i<5;i++) fSumXZ[i] = 0;
  fSumZZ = 0;
  fNUsed = 0;
  fConv = kFALSE;
}

AliTrackFitterStraight::AliTrackFitterStraight(const AliTrackFitterStraight &fitter):
  AliTrackFitter(fitter)
{
  //
  // copy constructor
  //
  fAlpha = fitter.fAlpha;
  for (Int_t i=0;i<5;i++) fSumXY[i]  = fitter.fSumXY[i];
  fSumYY = fitter.fSumYY;
  for (Int_t i=0;i<5;i++) fSumXZ[i]  = fitter.fSumXZ[i];
  fSumZZ = fitter.fSumZZ;
  fNUsed = fitter.fNUsed;
  fConv = fitter.fConv;
}

//_____________________________________________________________________________
AliTrackFitterStraight &AliTrackFitterStraight::operator =(const AliTrackFitterStraight& fitter)
{
  // assignment operator
  //
  if(this==&fitter) return *this;
  ((AliTrackFitter *)this)->operator=(fitter);

  fAlpha = fitter.fAlpha;
  for (Int_t i=0;i<5;i++) fSumXY[i]  = fitter.fSumXY[i];
  fSumYY = fitter.fSumYY;
  for (Int_t i=0;i<5;i++) fSumXZ[i]  = fitter.fSumXZ[i];
  fSumZZ = fitter.fSumZZ;
  fNUsed = fitter.fNUsed;
  fConv = fitter.fConv;

  return *this;
}

AliTrackFitterStraight::~AliTrackFitterStraight()
{
  // destructor
  //
}

void AliTrackFitterStraight::Reset()
{
  // Reset the track parameters and
  // sums
  AliTrackFitter::Reset();
  fAlpha = 0.;
  for (Int_t i=0;i<5;i++) fSumXY[i] = 0;
  fSumYY = 0;
  for (Int_t i=0;i<5;i++) fSumXZ[i] = 0;
  fSumZZ = 0;
  fNUsed = 0;
  fConv =kFALSE;
}

Bool_t AliTrackFitterStraight::Fit(const TArrayI *volIds,const TArrayI *volIdsFit,
				 AliAlignObj::ELayerID layerRangeMin,
				 AliAlignObj::ELayerID layerRangeMax)
{
  // Fit the track points. The method takes as an input
  // the set of id's (volids) of the volumes in which
  // one wants to calculate the residuals.
  // The following parameters are used to define the
  // range of volumes to be used in the fitting
  // As a result two AliTrackPointArray's obects are filled.
  // The first one contains the space points with
  // volume id's from volids list. The second array of points represents
  // the track extrapolations corresponding to the space points
  // in the first array. The two arrays can be used to find
  // the residuals in the volids and consequently construct a
  // chi2 function to be minimized during the alignment
  // procedures. For the moment the track extrapolation is taken
  // at the space-point reference plane. The reference plane is
  // found using the covariance matrix of the point
  // (assuming sigma(x)=0 at the reference coordinate system.

  Reset();

  Int_t npoints = fPoints->GetNPoints();
  if (npoints < 2) return kFALSE;

  Bool_t isAlphaCalc = kFALSE;
  AliTrackPoint p,plocal;

  Int_t npVolId = 0;
  fNUsed = 0;
  Int_t *pindex = new Int_t[npoints];
  for (Int_t ipoint = 0; ipoint < npoints; ipoint++)
    {
      fPoints->GetPoint(p,ipoint);
      UShort_t iVolId = p.GetVolumeID();
      if (FindVolId(volIds,iVolId)) {
	pindex[npVolId] = ipoint;
	npVolId++;
      }
      if (volIdsFit != 0x0) {
	if (!FindVolId(volIdsFit,iVolId)) continue;
      }
      else {
	if (iVolId < AliAlignObj::LayerToVolUID(layerRangeMin,0) ||
	    iVolId > AliAlignObj::LayerToVolUID(layerRangeMax,
						AliAlignObj::LayerSize(layerRangeMax-
								       AliAlignObj::kFirstLayer))) continue;
      }
      if (!isAlphaCalc) {
	fAlpha = p.GetAngle();
	isAlphaCalc = kTRUE;
      }
      plocal = p.Rotate(fAlpha);
      AddPoint(plocal.GetX(),plocal.GetY(),plocal.GetZ(),
	       TMath::Sqrt(plocal.GetCov()[3]),TMath::Sqrt(plocal.GetCov()[5]));
      fNUsed++;
    }

  if (fNUsed < 2) {
    delete [] pindex;
    return kFALSE;
  }

  Update();

  if (!fConv) {
    delete [] pindex;
    return kFALSE;
  }

  if (fNUsed < fMinNPoints ) {
    delete [] pindex;
    return kFALSE;
  }

  fPVolId = new AliTrackPointArray(npVolId);
  fPTrack = new AliTrackPointArray(npVolId);
  AliTrackPoint p2;
  for (Int_t ipoint = 0; ipoint < npVolId; ipoint++)
    {
      Int_t index = pindex[ipoint];
      fPoints->GetPoint(p,index);
      if (GetPCA(p,p2)) {
	Float_t xyz[3],xyz2[3];
	p.GetXYZ(xyz); p2.GetXYZ(xyz2);
	//	printf("residuals %f %d %d %f %f %f %f %f %f\n",fChi2,fNUsed,fConv,xyz[0],xyz[1],xyz[2],xyz2[0]-xyz[0],xyz2[1]-xyz[1],xyz2[2]-xyz[2]);
	fPVolId->AddPoint(ipoint,&p);
	fPTrack->AddPoint(ipoint,&p2);
      }
    }  

  delete [] pindex;

  return kTRUE;
}

void AliTrackFitterStraight::AddPoint(Float_t x, Float_t y, Float_t z, Float_t sy, Float_t sz)
{
  // Straight track fitter
  // The method add a point to the sums
  // used to extract track parameters

  //
  // XY part
  //
  Double_t weight = 1./(sy*sy);
  fSumXY[0] +=weight;
  fSumXY[1] +=x*weight;      fSumXY[2] +=x*x*weight;
  fSumXY[3] +=y*weight;      fSumXY[4] +=x*y*weight;
  fSumYY += y*y*weight;
  //
  // XZ part
  //
  weight = 1./(sz*sz);
  fSumXZ[0] +=weight;
  fSumXZ[1] +=x*weight;      fSumXZ[2] +=x*x*weight;
  fSumXZ[3] +=z*weight;      fSumXZ[4] +=x*z*weight;
  fSumZZ += z*z*weight;
}

void AliTrackFitterStraight::Update(){
  //
  //  Track fitter update
  //
  //
  for (Int_t i=0;i<6;i++)fParams[i]=0;
  fChi2 = 0;
  fNdf = 0;
  Int_t conv=0;
  //
  // XY part
  //
  TMatrixDSym     smatrix(2);
  TMatrixD        sums(1,2);
  smatrix(0,0) = fSumXY[0]; smatrix(1,1)=fSumXY[2];
  smatrix(0,1) = fSumXY[1];
  sums(0,0)    = fSumXY[3]; sums(0,1)   =fSumXY[4];
  smatrix.Invert();
  if (smatrix.IsValid()){
    for (Int_t i=0;i<2;i++)
      for (Int_t j=0;j<=i;j++){
	(*fCov)(i,j)=smatrix(i,j);
      }
    TMatrixD  res = sums*smatrix;
    fParams[0] = res(0,0);
    fParams[1] = res(0,1);
    TMatrixD  tmp = res*sums.T();
    fChi2 += fSumYY - tmp(0,0);
    fNdf  += fNUsed - 2;
    conv++;
  }
  //
  // XZ part
  //
  TMatrixDSym     smatrixz(2);
  TMatrixD        sumsxz(1,2);
  smatrixz(0,0) = fSumXZ[0]; smatrixz(1,1) = fSumXZ[2];
  smatrixz(0,1) = fSumXZ[1];
  sumsxz(0,0)   = fSumXZ[3]; sumsxz(0,1)   = fSumXZ[4];
  smatrixz.Invert();
  if (smatrixz.IsValid()){
    TMatrixD res = sumsxz*smatrixz;
    fParams[2] = res(0,0);
    fParams[3] = res(0,1);
    fParams[4] = fParams[5] = 0;
    for (Int_t i=0;i<2;i++)
      for (Int_t j=0;j<=i;j++){
	(*fCov)(i+2,j+2)=smatrixz(i,j);
      }
    TMatrixD  tmp = res*sumsxz.T();
    fChi2 += fSumZZ - tmp(0,0);
    fNdf  += fNUsed - 2;
    conv++;
  }

  if (conv>1)
    fConv =kTRUE;
  else
    fConv=kFALSE;
}

Double_t AliTrackFitterStraight::GetYat(Double_t x) const {
  if (!fConv) return 0.;
  return (fParams[0]+x*fParams[1]);
}

Double_t AliTrackFitterStraight::GetDYat(Double_t x) const {
  if (!fConv) return 0.;
  return fParams[1]+0.*x;
}


Double_t AliTrackFitterStraight::GetZat(Double_t x) const {
  if (!fConv) return 0.;
  return (fParams[2]+x*fParams[3]);
}

Double_t AliTrackFitterStraight::GetDZat(Double_t x) const {
  if (!fConv) return 0.;
  return fParams[3]+0.*x;
}

Bool_t AliTrackFitterStraight::GetXYZat(Double_t r, Float_t *xyz) const {
  if (!fConv) return kFALSE;
  Double_t y = (fParams[0]+r*fParams[1]);
  Double_t z = (fParams[2]+r*fParams[3]);

  Double_t sin = TMath::Sin(fAlpha);
  Double_t cos = TMath::Cos(fAlpha);
  xyz[0] = r*cos - y*sin;
  xyz[1] = y*cos + r*sin;
  xyz[2] = z;

  return kTRUE;
}

Bool_t AliTrackFitterStraight::GetPCA(const AliTrackPoint &p, AliTrackPoint &p2) const
{
  // Get the closest to a given spacepoint track trajectory point
  // Look for details in the description of the Fit() method

  if (!fConv) return kFALSE;

  // First X and Y coordinates
  Double_t sin = TMath::Sin(fAlpha);
  Double_t cos = TMath::Cos(fAlpha);
  // Track parameters in the global coordinate system
  Double_t x0 = -fParams[0]*sin;
  Double_t y0 =  fParams[0]*cos;
  if ((cos - fParams[1]*sin) == 0) return kFALSE;
  Double_t dydx = (fParams[1]*cos + sin)/(cos - fParams[1]*sin);

  // Define space-point refence plane
  Double_t alphap = p.GetAngle();
  Double_t sinp = TMath::Sin(alphap);
  Double_t cosp = TMath::Cos(alphap);
  Double_t x  = p.GetX()*cosp + p.GetY()*sinp;
  //  Double_t y  = p.GetY()*cosp - p.GetX()*sinp;
  Double_t x0p= x0*cosp + y0*sinp;
  Double_t y0p= y0*cosp - x0*sinp;
  if ((cos + dydx*sin) == 0) return kFALSE;
  Double_t dydxp = (dydx*cos - sin)/(cos + dydx*sin);
  Double_t yprime = y0p + dydxp*(x-x0p);

  // Back to the global coordinate system
  Double_t xsecond = x*cosp - yprime*sinp;
  Double_t ysecond = yprime*cosp + x*sinp;

  // Now Z coordinate and track angles
  Double_t x2 = xsecond*cos + ysecond*sin;
  Double_t zsecond = GetZat(x2);
  Double_t dydx2 = fParams[1];
  Double_t dzdx = fParams[3];

  // Fill the cov matrix of the track extrapolation point
  Double_t cov[6] = {0,0,0,0,0,0};
  Double_t sigmax = 100*100.;
  cov[0] = sigmax;             cov[1] = sigmax*dydx2;      cov[2] = sigmax*dzdx;
  cov[3] = sigmax*dydx2*dydx2; cov[4] = sigmax*dydx2*dzdx;
  cov[5] = sigmax*dzdx*dzdx;

  Float_t  newcov[6];
  newcov[0] = cov[0]*cos*cos-
            2*cov[1]*sin*cos+
              cov[3]*sin*sin;
  newcov[1] = cov[1]*(cos*cos-sin*sin)-
             (cov[3]-cov[0])*sin*cos;
  newcov[2] = cov[2]*cos-
              cov[4]*sin;
  newcov[3] = cov[0]*sin*sin+
            2*cov[1]*sin*cos+
              cov[3]*cos*cos;
  newcov[4] = cov[4]*cos+
              cov[2]*sin;
  newcov[5] = cov[5];

  p2.SetXYZ(xsecond,ysecond,zsecond,newcov);

  return kTRUE;
}
Commit	Line	Data
cc345ce3	1	#include "TMatrixDSym.h"
	2	#include "TMatrixD.h"
	3	#include "AliTrackFitterStraight.h"
	4
	5	ClassImp(AliTrackFitterStraight)
	6
	7	AliTrackFitterStraight::AliTrackFitterStraight():
	8	AliTrackFitter()
	9	{
	10	//
	11	// default constructor
	12	//
	13	fAlpha = 0.;
	14	for (Int_t i=0;i<5;i++) fSumXY[i] = 0;
	15	fSumYY = 0;
	16	for (Int_t i=0;i<5;i++) fSumXZ[i] = 0;
	17	fSumZZ = 0;
	18	fNUsed = 0;
	19	fConv = kFALSE;
	20	}
	21
	22
	23	AliTrackFitterStraight::AliTrackFitterStraight(AliTrackPointArray *array, Bool_t owner):
	24	AliTrackFitter(array,owner)
	25	{
	26	//
	27	// Constructor
	28	//
	29	fAlpha = 0.;
	30	for (Int_t i=0;i<5;i++) fSumXY[i] = 0;
	31	fSumYY = 0;
	32	for (Int_t i=0;i<5;i++) fSumXZ[i] = 0;
	33	fSumZZ = 0;
	34	fNUsed = 0;
	35	fConv = kFALSE;
	36	}
	37
	38	AliTrackFitterStraight::AliTrackFitterStraight(const AliTrackFitterStraight &fitter):
	39	AliTrackFitter(fitter)
	40	{
	41	//
	42	// copy constructor
	43	//
	44	fAlpha = fitter.fAlpha;
	45	for (Int_t i=0;i<5;i++) fSumXY[i] = fitter.fSumXY[i];
	46	fSumYY = fitter.fSumYY;
	47	for (Int_t i=0;i<5;i++) fSumXZ[i] = fitter.fSumXZ[i];
	48	fSumZZ = fitter.fSumZZ;
	49	fNUsed = fitter.fNUsed;
	50	fConv = fitter.fConv;
	51	}
	52
	53	//_____________________________________________________________________________
	54	AliTrackFitterStraight &AliTrackFitterStraight::operator =(const AliTrackFitterStraight& fitter)
	55	{
	56	// assignment operator
	57	//
	58	if(this==&fitter) return *this;
	59	((AliTrackFitter *)this)->operator=(fitter);
	60
	61	fAlpha = fitter.fAlpha;
	62	for (Int_t i=0;i<5;i++) fSumXY[i] = fitter.fSumXY[i];
	63	fSumYY = fitter.fSumYY;
	64	for (Int_t i=0;i<5;i++) fSumXZ[i] = fitter.fSumXZ[i];
65	fSumZZ = fitter.fSumZZ;
66	fNUsed = fitter.fNUsed;
67	fConv = fitter.fConv;
68
69	return *this;
70	}
71
72	AliTrackFitterStraight::~AliTrackFitterStraight()
73	{
74	// destructor
75	//
76	}
77
78	void AliTrackFitterStraight::Reset()
79	{
80	// Reset the track parameters and
81	// sums
82	AliTrackFitter::Reset();
83	fAlpha = 0.;
84	for (Int_t i=0;i<5;i++) fSumXY[i] = 0;
85	fSumYY = 0;
86	for (Int_t i=0;i<5;i++) fSumXZ[i] = 0;
87	fSumZZ = 0;
88	fNUsed = 0;
89	fConv =kFALSE;
90	}
91
92	Bool_t AliTrackFitterStraight::Fit(const TArrayI volIds,const TArrayI volIdsFit,
93	AliAlignObj::ELayerID layerRangeMin,
94	AliAlignObj::ELayerID layerRangeMax)
95	{
96	// Fit the track points. The method takes as an input
97	// the set of id's (volids) of the volumes in which
98	// one wants to calculate the residuals.
99	// The following parameters are used to define the
100	// range of volumes to be used in the fitting
101	// As a result two AliTrackPointArray's obects are filled.
102	// The first one contains the space points with
103	// volume id's from volids list. The second array of points represents
104	// the track extrapolations corresponding to the space points
105	// in the first array. The two arrays can be used to find
106	// the residuals in the volids and consequently construct a
107	// chi2 function to be minimized during the alignment
108	// procedures. For the moment the track extrapolation is taken
109	// at the space-point reference plane. The reference plane is
110	// found using the covariance matrix of the point
111	// (assuming sigma(x)=0 at the reference coordinate system.
112
113	Reset();
114
115	Int_t npoints = fPoints->GetNPoints();
116	if (npoints < 2) return kFALSE;
117
118	Bool_t isAlphaCalc = kFALSE;
119	AliTrackPoint p,plocal;
120
121	Int_t npVolId = 0;
122	fNUsed = 0;
123	Int_t *pindex = new Int_t[npoints];
124	for (Int_t ipoint = 0; ipoint < npoints; ipoint++)
125	{
126	fPoints->GetPoint(p,ipoint);
127	UShort_t iVolId = p.GetVolumeID();
128	if (FindVolId(volIds,iVolId)) {
129	pindex[npVolId] = ipoint;
130	npVolId++;
131	}
132	if (volIdsFit != 0x0) {
133	if (!FindVolId(volIdsFit,iVolId)) continue;
134	}
135	else {
136	if (iVolId < AliAlignObj::LayerToVolUID(layerRangeMin,0) \|\|
137	iVolId > AliAlignObj::LayerToVolUID(layerRangeMax,
138	AliAlignObj::LayerSize(layerRangeMax-
139	AliAlignObj::kFirstLayer))) continue;
140	}
141	if (!isAlphaCalc) {
142	fAlpha = p.GetAngle();
143	isAlphaCalc = kTRUE;
144	}
145	plocal = p.Rotate(fAlpha);
146	AddPoint(plocal.GetX(),plocal.GetY(),plocal.GetZ(),
147	TMath::Sqrt(plocal.GetCov()[3]),TMath::Sqrt(plocal.GetCov()[5]));
148	fNUsed++;
149	}
150
151	if (fNUsed < 2) {
152	delete [] pindex;
153	return kFALSE;
154	}
155
156	Update();
157
158	if (!fConv) {
159	delete [] pindex;
160	return kFALSE;
161	}
162
163	if (fNUsed < fMinNPoints ) {
164	delete [] pindex;
165	return kFALSE;
166	}
167
168	fPVolId = new AliTrackPointArray(npVolId);
169	fPTrack = new AliTrackPointArray(npVolId);
170	AliTrackPoint p2;
171	for (Int_t ipoint = 0; ipoint < npVolId; ipoint++)
172	{
173	Int_t index = pindex[ipoint];
174	fPoints->GetPoint(p,index);
175	if (GetPCA(p,p2)) {
176	Float_t xyz[3],xyz2[3];
177	p.GetXYZ(xyz); p2.GetXYZ(xyz2);
178	// printf("residuals %f %d %d %f %f %f %f %f %f\n",fChi2,fNUsed,fConv,xyz[0],xyz[1],xyz[2],xyz2[0]-xyz[0],xyz2[1]-xyz[1],xyz2[2]-xyz[2]);
179	fPVolId->AddPoint(ipoint,&p);
180	fPTrack->AddPoint(ipoint,&p2);
181	}
182	}
183
184	delete [] pindex;
185
186	return kTRUE;
187	}
188
189	void AliTrackFitterStraight::AddPoint(Float_t x, Float_t y, Float_t z, Float_t sy, Float_t sz)
190	{
191	// Straight track fitter
192	// The method add a point to the sums
193	// used to extract track parameters
194
195	//
196	// XY part
197	//
198	Double_t weight = 1./(sy*sy);
199	fSumXY[0] +=weight;
200	fSumXY[1] +=xweight; fSumXY[2] +=xx*weight;
201	fSumXY[3] +=yweight; fSumXY[4] +=xy*weight;
202	fSumYY += yyweight;
203	//
204	// XZ part
205	//
206	weight = 1./(sz*sz);
207	fSumXZ[0] +=weight;
208	fSumXZ[1] +=xweight; fSumXZ[2] +=xx*weight;
209	fSumXZ[3] +=zweight; fSumXZ[4] +=xz*weight;
210	fSumZZ += zzweight;
211	}
212
213	void AliTrackFitterStraight::Update(){
214	//
215	// Track fitter update
216	//
217	//
218	for (Int_t i=0;i<6;i++)fParams[i]=0;
219	fChi2 = 0;
220	fNdf = 0;
221	Int_t conv=0;
222	//
223	// XY part
224	//
225	TMatrixDSym smatrix(2);
226	TMatrixD sums(1,2);
227	smatrix(0,0) = fSumXY[0]; smatrix(1,1)=fSumXY[2];
228	smatrix(0,1) = fSumXY[1];
229	sums(0,0) = fSumXY[3]; sums(0,1) =fSumXY[4];
230	smatrix.Invert();
231	if (smatrix.IsValid()){
232	for (Int_t i=0;i<2;i++)
233	for (Int_t j=0;j<=i;j++){
234	(*fCov)(i,j)=smatrix(i,j);
235	}
236	TMatrixD res = sums*smatrix;
237	fParams[0] = res(0,0);
238	fParams[1] = res(0,1);
239	TMatrixD tmp = res*sums.T();
240	fChi2 += fSumYY - tmp(0,0);
241	fNdf += fNUsed - 2;
242	conv++;
243	}
244	//
245	// XZ part
246	//
247	TMatrixDSym smatrixz(2);
248	TMatrixD sumsxz(1,2);
249	smatrixz(0,0) = fSumXZ[0]; smatrixz(1,1) = fSumXZ[2];
250	smatrixz(0,1) = fSumXZ[1];
251	sumsxz(0,0) = fSumXZ[3]; sumsxz(0,1) = fSumXZ[4];
252	smatrixz.Invert();
253	if (smatrixz.IsValid()){
254	TMatrixD res = sumsxz*smatrixz;
255	fParams[2] = res(0,0);
256	fParams[3] = res(0,1);
257	fParams[4] = fParams[5] = 0;
258	for (Int_t i=0;i<2;i++)
259	for (Int_t j=0;j<=i;j++){
260	(*fCov)(i+2,j+2)=smatrixz(i,j);
261	}
262	TMatrixD tmp = res*sumsxz.T();
263	fChi2 += fSumZZ - tmp(0,0);
264	fNdf += fNUsed - 2;
265	conv++;
266	}
267
268	if (conv>1)
269	fConv =kTRUE;
270	else
271	fConv=kFALSE;
272	}
273
274	Double_t AliTrackFitterStraight::GetYat(Double_t x) const {
275	if (!fConv) return 0.;
276	return (fParams[0]+x*fParams[1]);
277	}
278
279	Double_t AliTrackFitterStraight::GetDYat(Double_t x) const {
280	if (!fConv) return 0.;
281	return fParams[1]+0.*x;
282	}
283
284
285
286	Double_t AliTrackFitterStraight::GetZat(Double_t x) const {
287	if (!fConv) return 0.;
288	return (fParams[2]+x*fParams[3]);
289	}
290
291	Double_t AliTrackFitterStraight::GetDZat(Double_t x) const {
292	if (!fConv) return 0.;
293	return fParams[3]+0.*x;
294	}
295
296	Bool_t AliTrackFitterStraight::GetXYZat(Double_t r, Float_t *xyz) const {
297	if (!fConv) return kFALSE;
298	Double_t y = (fParams[0]+r*fParams[1]);
299	Double_t z = (fParams[2]+r*fParams[3]);
300
301	Double_t sin = TMath::Sin(fAlpha);
302	Double_t cos = TMath::Cos(fAlpha);
303	xyz[0] = rcos - ysin;
304	xyz[1] = ycos + rsin;
305	xyz[2] = z;
306
307	return kTRUE;
308	}
309
310	Bool_t AliTrackFitterStraight::GetPCA(const AliTrackPoint &p, AliTrackPoint &p2) const
311	{
312	// Get the closest to a given spacepoint track trajectory point
313	// Look for details in the description of the Fit() method
314
315	if (!fConv) return kFALSE;
316
317	// First X and Y coordinates
318	Double_t sin = TMath::Sin(fAlpha);
319	Double_t cos = TMath::Cos(fAlpha);
320	// Track parameters in the global coordinate system
321	Double_t x0 = -fParams[0]*sin;
322	Double_t y0 = fParams[0]*cos;
323	if ((cos - fParams[1]*sin) == 0) return kFALSE;
324	Double_t dydx = (fParams[1]cos + sin)/(cos - fParams[1]sin);
325
326	// Define space-point refence plane
327	Double_t alphap = p.GetAngle();
328	Double_t sinp = TMath::Sin(alphap);
329	Double_t cosp = TMath::Cos(alphap);
330	Double_t x = p.GetX()cosp + p.GetY()sinp;
331	// Double_t y = p.GetY()cosp - p.GetX()sinp;
332	Double_t x0p= x0cosp + y0sinp;
333	Double_t y0p= y0cosp - x0sinp;
334	if ((cos + dydx*sin) == 0) return kFALSE;
335	Double_t dydxp = (dydxcos - sin)/(cos + dydxsin);
336	Double_t yprime = y0p + dydxp*(x-x0p);
337
338	// Back to the global coordinate system
339	Double_t xsecond = xcosp - yprimesinp;
340	Double_t ysecond = yprimecosp + xsinp;
341
342	// Now Z coordinate and track angles
343	Double_t x2 = xsecondcos + ysecondsin;
344	Double_t zsecond = GetZat(x2);
345	Double_t dydx2 = fParams[1];
346	Double_t dzdx = fParams[3];
347
348	// Fill the cov matrix of the track extrapolation point
349	Double_t cov[6] = {0,0,0,0,0,0};
350	Double_t sigmax = 100*100.;
351	cov[0] = sigmax; cov[1] = sigmaxdydx2; cov[2] = sigmaxdzdx;
352	cov[3] = sigmaxdydx2dydx2; cov[4] = sigmaxdydx2dzdx;
353	cov[5] = sigmaxdzdxdzdx;
354
355	Float_t newcov[6];
356	newcov[0] = cov[0]coscos-
357	2cov[1]sin*cos+
358	cov[3]sinsin;
359	newcov[1] = cov[1](coscos-sin*sin)-
360	(cov[3]-cov[0])sincos;
361	newcov[2] = cov[2]*cos-
362	cov[4]*sin;
363	newcov[3] = cov[0]sinsin+
364	2cov[1]sin*cos+
365	cov[3]coscos;
366	newcov[4] = cov[4]*cos+
367	cov[2]*sin;
368	newcov[5] = cov[5];
369
370	p2.SetXYZ(xsecond,ysecond,zsecond,newcov);
371
372	return kTRUE;
373	}