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 //-------------------------------------------------------------------------
17 // Implementation of the ITS track class
19 // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch
20 // dEdx analysis by: Boris Batyunya, JINR, Boris.Batiounia@cern.ch
21 //-------------------------------------------------------------------------
27 #include "AliCluster.h"
28 #include "AliTPCtrack.h"
29 #include "AliITStrackV2.h"
31 ClassImp(AliITStrackV2)
35 //____________________________________________________________________________
36 AliITStrackV2::AliITStrackV2():AliKalmanTrack(),
61 for(Int_t i=0; i<kMaxLayer; i++) fIndex[i]=0;
62 for(Int_t i=0; i<4; i++) fdEdxSample[i]=0;
64 //____________________________________________________________________________
65 AliITStrackV2::AliITStrackV2(const AliTPCtrack& t) throw (const Char_t *) :
67 //------------------------------------------------------------------
68 //Conversion TPC track -> ITS track
69 //------------------------------------------------------------------
71 SetNumberOfClusters(0);
76 fAlpha = t.GetAlpha();
77 if (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
78 else if (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();
80 //Conversion of the track parameters
81 Double_t x,p[5]; t.GetExternalParameters(x,p);
82 fX=x; x=GetConvConst();
89 //Conversion of the covariance matrix
90 Double_t c[15]; t.GetExternalCovariance(c);
93 fC10=c[1 ]; fC11=c[2 ];
94 fC20=c[3 ]; fC21=c[4 ]; fC22=c[5 ];
95 fC30=c[6 ]; fC31=c[7 ]; fC32=c[8 ]; fC33=c[9 ];
96 fC40=c[10]/x; fC41=c[11]/x; fC42=c[12]/x; fC43=c[13]/x; fC44=c[14]/x/x;
98 if (!Invariant()) throw "AliITStrackV2: conversion failed !\n";
102 //____________________________________________________________________________
103 AliITStrackV2::AliITStrackV2(const AliITStrackV2& t) : AliKalmanTrack(t) {
104 //------------------------------------------------------------------
106 //------------------------------------------------------------------
111 fP0=t.fP0; fP1=t.fP1; fP2=t.fP2; fP3=t.fP3; fP4=t.fP4;
114 fC10=t.fC10; fC11=t.fC11;
115 fC20=t.fC20; fC21=t.fC21; fC22=t.fC22;
116 fC30=t.fC30; fC31=t.fC31; fC32=t.fC32; fC33=t.fC33;
117 fC40=t.fC40; fC41=t.fC41; fC42=t.fC42; fC43=t.fC43; fC44=t.fC44;
119 Int_t n=GetNumberOfClusters();
120 for (Int_t i=0; i<n; i++) {
121 fIndex[i]=t.fIndex[i];
122 if (i<4) fdEdxSample[i]=t.fdEdxSample[i];
126 //_____________________________________________________________________________
127 Int_t AliITStrackV2::Compare(const TObject *o) const {
128 //-----------------------------------------------------------------
129 // This function compares tracks according to the their curvature
130 //-----------------------------------------------------------------
131 AliITStrackV2 *t=(AliITStrackV2*)o;
132 //Double_t co=TMath::Abs(t->Get1Pt());
133 //Double_t c =TMath::Abs(Get1Pt());
134 Double_t co=t->GetSigmaY2()*t->GetSigmaZ2();
135 Double_t c =GetSigmaY2()*GetSigmaZ2();
137 else if (c<co) return -1;
141 //_____________________________________________________________________________
142 void AliITStrackV2::GetExternalCovariance(Double_t cc[15]) const {
143 //-------------------------------------------------------------------------
144 // This function returns an external representation of the covriance matrix.
145 // (See comments in AliTPCtrack.h about external track representation)
146 //-------------------------------------------------------------------------
147 Double_t a=GetConvConst();
150 cc[1 ]=fC10; cc[2 ]=fC11;
151 cc[3 ]=fC20; cc[4 ]=fC21; cc[5 ]=fC22;
152 cc[6 ]=fC30; cc[7 ]=fC31; cc[8 ]=fC32; cc[9 ]=fC33;
153 cc[10]=fC40*a; cc[11]=fC41*a; cc[12]=fC42*a; cc[13]=fC43*a; cc[14]=fC44*a*a;
156 //____________________________________________________________________________
157 Int_t AliITStrackV2::PropagateToVertex(Double_t d,Double_t x0) {
158 //------------------------------------------------------------------
159 //This function propagates a track to the minimal distance from the origin
160 //------------------------------------------------------------------
161 //Double_t xv=fP2*(fX*fP2 - fP0*TMath::Sqrt(1.- fP2*fP2)); //linear approxim.
162 Double_t tgf=-(fP4*fX - fP2)/(fP4*fP0 + TMath::Sqrt(1 - fP2*fP2));
163 Double_t snf=tgf/TMath::Sqrt(1.+ tgf*tgf);
164 Double_t xv=(snf - fP2)/fP4 + fX;
165 return PropagateTo(xv,d,x0);
168 //____________________________________________________________________________
169 Int_t AliITStrackV2::
170 GetGlobalXYZat(Double_t xk, Double_t &x, Double_t &y, Double_t &z) const {
171 //------------------------------------------------------------------
172 //This function returns a track position in the global system
173 //------------------------------------------------------------------
175 Double_t f1=fP2, f2=f1 + fP4*dx;
176 if (TMath::Abs(f2) >= 0.9999) {
177 Int_t n=GetNumberOfClusters();
179 Warning("GetGlobalXYZat","Propagation failed (%d) !\n",n);
183 Double_t r1=sqrt(1.- f1*f1), r2=sqrt(1.- f2*f2);
185 Double_t yk = fP0 + dx*(f1+f2)/(r1+r2);
186 Double_t zk = fP1 + dx*(f1+f2)/(f1*r2 + f2*r1)*fP3;
188 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
196 //_____________________________________________________________________________
197 Double_t AliITStrackV2::GetPredictedChi2(const AliCluster *c) const
199 //-----------------------------------------------------------------
200 // This function calculates a predicted chi2 increment.
201 //-----------------------------------------------------------------
202 Double_t r00=c->GetSigmaY2(), r01=0., r11=c->GetSigmaZ2();
203 r00+=fC00; r01+=fC10; r11+=fC11;
205 Double_t det=r00*r11 - r01*r01;
206 if (TMath::Abs(det) < 1.e-30) {
207 Int_t n=GetNumberOfClusters();
209 Warning("GetPredictedChi2","Singular matrix (%d) !\n",n);
212 Double_t tmp=r00; r00=r11; r11=tmp; r01=-r01;
214 Double_t dy=c->GetY() - fP0, dz=c->GetZ() - fP1;
216 return (dy*r00*dy + 2*r01*dy*dz + dz*r11*dz)/det;
219 //____________________________________________________________________________
220 Int_t AliITStrackV2::CorrectForMaterial(Double_t d, Double_t x0) {
221 //------------------------------------------------------------------
222 //This function corrects the track parameters for crossed material
223 //------------------------------------------------------------------
224 Double_t p2=(1.+ GetTgl()*GetTgl())/(Get1Pt()*Get1Pt());
225 Double_t beta2=p2/(p2 + GetMass()*GetMass());
226 d*=TMath::Sqrt((1.+ fP3*fP3)/(1.- fP2*fP2));
228 //Multiple scattering******************
230 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(d);
231 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
232 fC22 += theta2*(1.- fP2*fP2)*(1. + fP3*fP3);
233 fC33 += theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
234 fC43 += theta2*fP3*fP4*(1. + fP3*fP3);
235 fC44 += theta2*fP3*fP4*fP3*fP4;
238 //Energy losses************************
241 Double_t dE=0.153e-3/beta2*(log(5940*beta2/(1-beta2)) - beta2)*d;
242 fP4*=(1.- sqrt(p2+GetMass()*GetMass())/p2*dE);
245 if (!Invariant()) return 0;
250 //____________________________________________________________________________
251 Int_t AliITStrackV2::PropagateTo(Double_t xk, Double_t d, Double_t x0) {
252 //------------------------------------------------------------------
253 //This function propagates a track
254 //------------------------------------------------------------------
255 Double_t x1=fX, x2=xk, dx=x2-x1;
256 Double_t f1=fP2, f2=f1 + fP4*dx;
257 if (TMath::Abs(f2) >= 0.9999) {
258 Int_t n=GetNumberOfClusters();
260 Warning("PropagateTo","Propagation failed !\n",n);
264 // old position [SR, GSI, 17.02.2003]
265 Double_t oldX = fX, oldY = fP0, oldZ = fP1;
267 Double_t r1=sqrt(1.- f1*f1), r2=sqrt(1.- f2*f2);
269 fP0 += dx*(f1+f2)/(r1+r2);
270 fP1 += dx*(f1+f2)/(f1*r2 + f2*r1)*fP3;
275 Double_t f02= dx/(r1*r1*r1);
276 Double_t f04=0.5*dx*dx/(r1*r1*r1);
277 Double_t f12= dx*fP3*f1/(r1*r1*r1);
278 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1);
283 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
284 Double_t b02=f24*fC40;
285 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
286 Double_t b12=f24*fC41;
287 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
288 Double_t b22=f24*fC42;
289 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
290 Double_t b42=f24*fC44;
291 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
292 Double_t b32=f24*fC43;
295 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
296 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
297 Double_t a22=f24*b42;
299 //F*C*Ft = C + (b + bt + a)
300 fC00 += b00 + b00 + a00;
301 fC10 += b10 + b01 + a01;
302 fC20 += b20 + b02 + a02;
305 fC11 += b11 + b11 + a11;
306 fC21 += b21 + b12 + a12;
309 fC22 += b22 + b22 + a22;
315 if (!CorrectForMaterial(d,x0)) return 0;
317 // Integrated Time [SR, GSI, 17.02.2003]
318 if (IsStartedTimeIntegral()) {
319 Double_t l2 = (fX-oldX)*(fX-oldX)+(fP0-oldY)*(fP0-oldY)+
320 (fP1-oldZ)*(fP1-oldZ);
321 AddTimeStep(TMath::Sqrt(l2));
328 //____________________________________________________________________________
329 Int_t AliITStrackV2::Update(const AliCluster* c, Double_t chi2, UInt_t index) {
330 //------------------------------------------------------------------
331 //This function updates track parameters
332 //------------------------------------------------------------------
333 Double_t p0=fP0,p1=fP1,p2=fP2,p3=fP3,p4=fP4;
335 Double_t c10=fC10, c11=fC11;
336 Double_t c20=fC20, c21=fC21, c22=fC22;
337 Double_t c30=fC30, c31=fC31, c32=fC32, c33=fC33;
338 Double_t c40=fC40, c41=fC41, c42=fC42, c43=fC43, c44=fC44;
341 Double_t r00=c->GetSigmaY2(), r01=0., r11=c->GetSigmaZ2();
342 r00+=fC00; r01+=fC10; r11+=fC11;
343 Double_t det=r00*r11 - r01*r01;
344 Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
346 Double_t k00=fC00*r00+fC10*r01, k01=fC00*r01+fC10*r11;
347 Double_t k10=fC10*r00+fC11*r01, k11=fC10*r01+fC11*r11;
348 Double_t k20=fC20*r00+fC21*r01, k21=fC20*r01+fC21*r11;
349 Double_t k30=fC30*r00+fC31*r01, k31=fC30*r01+fC31*r11;
350 Double_t k40=fC40*r00+fC41*r01, k41=fC40*r01+fC41*r11;
352 Double_t dy=c->GetY() - fP0, dz=c->GetZ() - fP1;
353 Double_t sf=fP2 + k20*dy + k21*dz;
355 fP0 += k00*dy + k01*dz;
356 fP1 += k10*dy + k11*dz;
358 fP3 += k30*dy + k31*dz;
359 fP4 += k40*dy + k41*dz;
361 Double_t c01=fC10, c02=fC20, c03=fC30, c04=fC40;
362 Double_t c12=fC21, c13=fC31, c14=fC41;
364 fC00-=k00*fC00+k01*fC10; fC10-=k00*c01+k01*fC11;
365 fC20-=k00*c02+k01*c12; fC30-=k00*c03+k01*c13;
366 fC40-=k00*c04+k01*c14;
368 fC11-=k10*c01+k11*fC11;
369 fC21-=k10*c02+k11*c12; fC31-=k10*c03+k11*c13;
370 fC41-=k10*c04+k11*c14;
372 fC22-=k20*c02+k21*c12; fC32-=k20*c03+k21*c13;
373 fC42-=k20*c04+k21*c14;
375 fC33-=k30*c03+k31*c13;
376 fC43-=k30*c04+k31*c14;
378 fC44-=k40*c04+k41*c14;
381 fP0=p0; fP1=p1; fP2=p2; fP3=p3; fP4=p4;
384 fC20=c20; fC21=c21; fC22=c22;
385 fC30=c30; fC31=c31; fC32=c32; fC33=c33;
386 fC40=c40; fC41=c41; fC42=c42; fC43=c43; fC44=c44;
390 Int_t n=GetNumberOfClusters();
392 SetNumberOfClusters(n+1);
393 SetChi2(GetChi2()+chi2);
398 Int_t AliITStrackV2::Invariant() const {
399 //------------------------------------------------------------------
400 // This function is for debugging purpose only
401 //------------------------------------------------------------------
402 Int_t n=GetNumberOfClusters();
404 if (TMath::Abs(fP2)>=0.9999){
405 if (n>kWARN) Warning("Invariant","fP2=%f\n",fP2);
408 if (fC00<=0 || fC00>9.) {
409 if (n>kWARN) Warning("Invariant","fC00=%f\n",fC00);
412 if (fC11<=0 || fC11>9.) {
413 if (n>kWARN) Warning("Invariant","fC11=%f\n",fC11);
416 if (fC22<=0 || fC22>1.) {
417 if (n>kWARN) Warning("Invariant","fC22=%f\n",fC22);
420 if (fC33<=0 || fC33>1.) {
421 if (n>kWARN) Warning("Invariant","fC33=%f\n",fC33);
424 if (fC44<=0 || fC44>6e-5) {
425 if (n>kWARN) Warning("Invariant","fC44=%f\n",fC44);
431 //____________________________________________________________________________
432 Int_t AliITStrackV2::Propagate(Double_t alp,Double_t xk) {
433 //------------------------------------------------------------------
434 //This function propagates a track
435 //------------------------------------------------------------------
436 Double_t alpha=fAlpha, x=fX;
437 Double_t p0=fP0,p1=fP1,p2=fP2,p3=fP3,p4=fP4;
439 Double_t c10=fC10, c11=fC11;
440 Double_t c20=fC20, c21=fC21, c22=fC22;
441 Double_t c30=fC30, c31=fC31, c32=fC32, c33=fC33;
442 Double_t c40=fC40, c41=fC41, c42=fC42, c43=fC43, c44=fC44;
444 if (alp < -TMath::Pi()) alp += 2*TMath::Pi();
445 else if (alp >= TMath::Pi()) alp -= 2*TMath::Pi();
446 Double_t ca=TMath::Cos(alp-fAlpha), sa=TMath::Sin(alp-fAlpha);
447 Double_t sf=fP2, cf=TMath::Sqrt(1.- fP2*fP2);
450 // **** rotation **********************
459 C(1,0)=c10; C(1,1)=c11;
460 C(2,0)=c20; C(2,1)=c21; C(2,2)=c22;
461 C(3,0)=c30; C(3,1)=c31; C(3,2)=c32; C(3,3)=c33;
462 C(4,0)=c40; C(4,1)=c41; C(4,2)=c42; C(4,3)=c43; C(4,4)=c44;
464 C(0,2)=C(2,0); C(1,2)=C(2,1);
465 C(0,3)=C(3,0); C(1,3)=C(3,1); C(2,3)=C(3,2);
466 C(0,4)=C(4,0); C(1,4)=C(4,1); C(2,4)=C(4,2); C(3,4)=C(4,3);
471 F(2,1)=F(4,3)=F(5,4)=1;
472 F(3,2)=ca + sf/cf*sa;
474 TMatrixD tmp(C,TMatrixD::kMult,TMatrixD(TMatrixD::kTransposed, F));
475 T=new TMatrixD(F,TMatrixD::kMult,tmp);
478 // **** translation ******************
481 Double_t f1=fP2, f2=f1 + fP4*dx;
482 if (TMath::Abs(f2) >= 0.9999) {
483 Int_t n=GetNumberOfClusters();
485 Warning("Propagate","Propagation failed (%d) !\n",n);
488 Double_t r1=TMath::Sqrt(1.- f1*f1), r2=TMath::Sqrt(1.- f2*f2);
491 fP0 += dx*(f1+f2)/(r1+r2);
492 fP1 += dx*(f1+f2)/(f1*r2 + f2*r1)*fP3;
496 F(0,1)=F(1,2)=F(2,3)=F(3,4)=F(4,5)=1;
497 F(0,3)=dx/(r1+r2)*(2+(f1+f2)*(f2/r2+f1/r1)/(r1+r2));
498 F(0,5)=dx*dx/(r1+r2)*(1+(f1+f2)*f2/(r1+r2));
499 F(1,3)=dx*fP3/(f1*r2 + f2*r1)*(2-(f1+f2)*(r2-f1*f2/r2+r1-f2*f1/r1)/(f1*r2 + f2*r1));
500 F(1,4)=dx*(f1+f2)/(f1*r2 + f2*r1);
501 F(1,5)=dx*dx*fP3/(f1*r2 + f2*r1)*(1-(f1+f2)*(-f1*f2/r2+r1)/(f1*r2 + f2*r1));
503 F(0,0)=-1/(r1+r2)*((f1+f2)+dx*fP4*(1+(f1+f2)/(r1+r2)*f2/r2));
504 F(1,0)=-fP3/(f1*r2 + f2*r1)*((f1+f2)+dx*fP4*(1+(f1+f2)/(f1*r2 + f2*r1)*(f1*f2/r2-r1)));
507 TMatrixD tmp(*T,TMatrixD::kMult,TMatrixD(TMatrixD::kTransposed, F));
509 TMatrixD C(F,TMatrixD::kMult,tmp);
512 fC10=C(1,0); fC11=C(1,1);
513 fC20=C(2,0); fC21=C(2,1); fC22=C(2,2);
514 fC30=C(3,0); fC31=C(3,1); fC32=C(3,2); fC33=C(3,3);
515 fC40=C(4,0); fC41=C(4,1); fC42=C(4,2); fC43=C(4,3); fC44=C(4,4);
520 fP0=p0; fP1=p1; fP2=p2; fP3=p3; fP4=p4;
523 fC20=c20; fC21=c21; fC22=c22;
524 fC30=c30; fC31=c31; fC32=c32; fC33=c33;
525 fC40=c40; fC41=c41; fC42=c42; fC43=c43; fC44=c44;
533 Double_t AliITStrackV2::GetD(Double_t x, Double_t y) const {
534 //------------------------------------------------------------------
535 // This function calculates the transverse impact parameter
536 // with respect to a point with global coordinates (x,y)
537 //------------------------------------------------------------------
538 Double_t xt=fX, yt=fP0;
540 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
541 Double_t a = x*cs + y*sn;
542 y = -x*sn + y*cs; x=a;
545 sn=fP4*xt - fP2; cs=fP4*yt + TMath::Sqrt(1.- fP2*fP2);
546 a=2*(xt*fP2 - yt*TMath::Sqrt(1.- fP2*fP2))-fP4*(xt*xt + yt*yt);
548 return a/(1 + TMath::Sqrt(sn*sn + cs*cs));
551 Int_t AliITStrackV2::Improve(Double_t x0,Double_t xyz[3],Double_t ers[3]) {
552 //------------------------------------------------------------------
553 //This function improves angular track parameters
554 //------------------------------------------------------------------
555 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
556 //Double_t xv = xyz[0]*cs + xyz[1]*sn; // vertex
557 Double_t yv =-xyz[0]*sn + xyz[1]*cs; // in the
558 Double_t zv = xyz[2]; // local frame
559 Double_t dy=fP0-yv, dz=fP1-zv;
560 Double_t r2=fX*fX+dy*dy;
561 Double_t p2=(1.+ GetTgl()*GetTgl())/(Get1Pt()*Get1Pt());
562 Double_t beta2=p2/(p2 + GetMass()*GetMass());
563 x0*=TMath::Sqrt((1.+ GetTgl()*GetTgl())/(1.- GetSnp()*GetSnp()));
564 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*x0;
565 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*x0*9.36*2.33;
567 Double_t parp=0.5*(fP4*fX + dy*TMath::Sqrt(4/r2-fP4*fP4));
568 Double_t sigma2p = theta2*(1.- GetSnp()*GetSnp())*(1. + GetTgl()*GetTgl());
569 sigma2p += fC00/r2*(1.- dy*dy/r2)*(1.- dy*dy/r2);
570 sigma2p += ers[1]*ers[1]/r2;
571 sigma2p += 0.25*fC44*fX*fX;
572 Double_t eps2p=sigma2p/(fC22+sigma2p);
573 fP0 += fC20/(fC22+sigma2p)*(parp-fP2);
574 fP2 = eps2p*fP2 + (1-eps2p)*parp;
579 Double_t parl=0.5*fP4*dz/TMath::ASin(0.5*fP4*TMath::Sqrt(r2));
580 Double_t sigma2l=theta2;
581 sigma2l += fC11/r2+fC00*dy*dy*dz*dz/(r2*r2*r2);
582 sigma2l += ers[2]*ers[2]/r2;
583 Double_t eps2l=sigma2l/(fC33+sigma2l);
584 fP1 += fC31/(fC33+sigma2l)*(parl-fP3);
585 fP4 += fC43/(fC33+sigma2l)*(parl-fP3);
586 fP3 = eps2l*fP3 + (1-eps2l)*parl;
587 fC33 *= eps2l; fC43 *= eps2l;
590 if (!Invariant()) return 0;
595 Int_t AliITStrackV2::Improve(Double_t x0,Double_t yv,Double_t zv) {
596 //------------------------------------------------------------------
597 //This function improves angular track parameters
598 //------------------------------------------------------------------
599 Double_t dy=fP0-yv, dz=fP1-zv;
600 Double_t r2=fX*fX+dy*dy;
601 Double_t p2=(1.+ GetTgl()*GetTgl())/(Get1Pt()*Get1Pt());
602 Double_t beta2=p2/(p2 + GetMass()*GetMass());
603 x0*=TMath::Sqrt((1.+ GetTgl()*GetTgl())/(1.- GetSnp()*GetSnp()));
604 //Double_t theta2=14.1*14.1/(beta2*p2*1e6)*x0;
605 Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*x0*9.36*2.33;
607 Double_t par=0.5*(fP4*fX + dy*TMath::Sqrt(4/r2-fP4*fP4));
608 Double_t sigma2 = theta2*(1.- GetSnp()*GetSnp())*(1. + GetTgl()*GetTgl());
609 sigma2 += fC00/r2*(1.- dy*dy/r2)*(1.- dy*dy/r2);
610 sigma2 += kSigmaYV*kSigmaYV/r2;
611 sigma2 += 0.25*fC44*fX*fX;
612 Double_t eps2=sigma2/(fC22+sigma2), eps=TMath::Sqrt(eps2);
613 if (10*r2*fC44<fC22) {
614 fP2 = eps2*fP2 + (1-eps2)*par;
615 fC22*=eps2; fC21*=eps; fC20*=eps; fC32*=eps; fC42*=eps;
618 par=0.5*fP4*dz/TMath::ASin(0.5*fP4*TMath::Sqrt(r2));
620 sigma2 += fC11/r2+fC00*dy*dy*dz*dz/(r2*r2*r2);
621 sigma2 += kSigmaZV*kSigmaZV/r2;
622 eps2=sigma2/(fC33+sigma2); eps=TMath::Sqrt(eps2);
624 fP3 = eps2*fP3 + (1-eps2)*par;
625 fC33*=eps2; fC32*=eps; fC31*=eps; fC30*=eps; fC43*=eps;
627 eps=TMath::Sqrt((1+fP3*fP3)/(1+tgl*tgl));
629 fC44*=eps*eps; fC43*=eps;fC42*=eps; fC41*=eps; fC40*=eps;
631 if (!Invariant()) return 0;
635 void AliITStrackV2::ResetCovariance() {
636 //------------------------------------------------------------------
637 //This function makes a track forget its history :)
638 //------------------------------------------------------------------
642 fC20=0.; fC21=0.; fC22*=10.;
643 fC30=0.; fC31=0.; fC32=0.; fC33*=10.;
644 fC40=0.; fC41=0.; fC42=0.; fC43=0.; fC44*=10.;
648 void AliITStrackV2::CookdEdx(Double_t low, Double_t up) {
649 //-----------------------------------------------------------------
650 // This function calculates dE/dX within the "low" and "up" cuts.
651 // Origin: Boris Batyunya, JINR, Boris.Batiounia@cern.ch
652 //-----------------------------------------------------------------
655 // The clusters order is: SSD-2, SSD-1, SDD-2, SDD-1, SPD-2, SPD-1
656 // Take only SSD and SDD
658 Int_t swap;//stupid sorting
661 for (i=0; i<nc-1; i++) {
662 if (fdEdxSample[i]<=fdEdxSample[i+1]) continue;
663 Float_t tmp=fdEdxSample[i];
664 fdEdxSample[i]=fdEdxSample[i+1]; fdEdxSample[i+1]=tmp;
669 Int_t nl=Int_t(low*nc), nu=Int_t(up*nc); //b.b. to take two lowest dEdX
670 // values from four ones choose
673 for (i=nl; i<nu; i++) dedx += fdEdxSample[i];