2 // Original: AliHLTConfMapFit.cxx,v 1.14 2005/06/14 10:55:21 cvetan
4 /**************************************************************************
5 * This file is property of and copyright by the ALICE HLT Project *
6 * ALICE Experiment at CERN, All rights reserved. *
8 * Primary Authors: Anders Vestbo, maintained by *
9 * Matthias Richter <Matthias.Richter@ift.uib.no> *
10 * for The ALICE HLT Project. *
12 * Permission to use, copy, modify and distribute this software and its *
13 * documentation strictly for non-commercial purposes is hereby granted *
14 * without fee, provided that the above copyright notice appears in all *
15 * copies and that both the copyright notice and this permission notice *
16 * appear in the supporting documentation. The authors make no claims *
17 * about the suitability of this software for any purpose. It is *
18 * provided "as is" without express or implied warranty. *
19 **************************************************************************/
21 /** @file AliHLTTPCConfMapFit.cxx
22 @author Anders Vestbo, maintained by Matthias Richter
24 @brief Fit class for conformal mapping tracking.
27 // see header file for class documentation //
29 // refer to README to build package //
31 // visit http://web.ift.uib.no/~kjeks/doc/alice-hlt //
33 #include "AliHLTTPCRootTypes.h"
34 #include "AliHLTTPCLogging.h"
35 #include "AliHLTTPCVertex.h"
36 #include "AliHLTTPCConfMapTrack.h"
37 #include "AliHLTTPCConfMapPoint.h"
38 #include "AliHLTTPCTransform.h"
39 #include "AliHLTTPCConfMapFit.h"
45 ClassImp(AliHLTTPCConfMapFit);
47 AliHLTTPCConfMapFit::AliHLTTPCConfMapFit()
55 AliHLTTPCConfMapFit::AliHLTTPCConfMapFit(AliHLTTPCConfMapTrack *track,AliHLTTPCVertex *vertex)
64 AliHLTTPCConfMapFit::~AliHLTTPCConfMapFit()
69 Int_t AliHLTTPCConfMapFit::FitHelix()
74 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitHelix","TrackFit")<<AliHLTTPCLog::kDec<<
75 "Problems during circle fit"<<ENDLOG;
80 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitHelix","TrackFit")<<AliHLTTPCLog::kDec<<
81 "Problems during line fit"<<ENDLOG;
87 Int_t AliHLTTPCConfMapFit::FitStraightLine() {
88 //fit the straight line
90 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitStraightLine","TrackFit")<<AliHLTTPCLog::kDec<<
91 "Problems during stright line fit in XY plane"<<ENDLOG;
95 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitStraightLine","TrackFit")<<AliHLTTPCLog::kDec<<
96 "Problems during stright line fit in SZ plane"<<ENDLOG;
102 Int_t AliHLTTPCConfMapFit::FitCircle()
104 //-----------------------------------------------------------------
105 //Fits circle parameters using algorithm
106 //described by ChErnov and Oskov in Computer Physics
109 //Written in FORTRAN by Jawluen Tang, Physics department , UT-Austin
110 //Moved to C by Pablo Yepes
111 //Moved to AliROOT by ASV.
112 //------------------------------------------------------------------
114 Double_t wsum = 0.0 ;
118 Int_t numOfHits = fTrack->GetNumberOfPoints();
120 // Loop over hits calculating average
123 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit())
126 AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
127 cHit->SetXYWeight( 1./ (Double_t)(cHit->GetXerr()*cHit->GetXerr() + cHit->GetYerr()*cHit->GetYerr()) );
128 wsum += cHit->GetXYWeight() ;
129 xav += cHit->GetXYWeight() * cHit->GetX() ;
130 yav += cHit->GetXYWeight() * cHit->GetY() ;
133 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitCircle","TrackFit")<<AliHLTTPCLog::kDec<<
134 "Mismatch of hits. Counter: "<<co<<" nHits: "<<numOfHits<<ENDLOG;
135 if (fTrack->ComesFromMainVertex() == true)
137 wsum += fVertex->GetXYWeight() ;
138 xav += fVertex->GetX() ;
139 yav += fVertex->GetY() ;
145 // CALCULATE <X**2>, <XY>, AND <Y**2> WITH <X> = 0, & <Y> = 0
147 Double_t xxav = 0.0 ;
148 Double_t xyav = 0.0 ;
149 Double_t yyav = 0.0 ;
152 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit())
154 //AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint *)hits->At(hit_counter);
155 AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
156 xi = cHit->GetX() - xav ;
157 yi = cHit->GetY() - yav ;
158 xxav += xi * xi * cHit->GetXYWeight() ;
159 xyav += xi * yi * cHit->GetXYWeight() ;
160 yyav += yi * yi * cHit->GetXYWeight() ;
163 if (fTrack->ComesFromMainVertex() == true)
165 xi = fVertex->GetX() - xav ;
166 yi = fVertex->GetY() - yav ;
167 xxav += xi * xi * fVertex->GetXYWeight() ;
168 xyav += xi * yi * fVertex->GetXYWeight() ;
169 yyav += yi * yi * fVertex->GetXYWeight() ;
175 //--> ROTATE COORDINATES SO THAT <XY> = 0
177 //--> SIGN(C**2 - S**2) = SIGN(XXAV - YYAV) >
178 //--> & > ==> NEW : (XXAV-YYAV) > 0
179 //--> SIGN(S) = SIGN(XYAV) >
181 Double_t a = fabs( xxav - yyav ) ;
182 Double_t b = 4.0 * xyav * xyav ;
184 Double_t asqpb = a * a + b ;
185 Double_t rasqpb = sqrt ( asqpb) ;
187 Double_t splus = 1.0 + a / rasqpb ;
188 Double_t sminus = b / (asqpb * splus) ;
190 splus = sqrt (0.5 * splus ) ;
191 sminus = sqrt (0.5 * sminus) ;
193 //-> FIRST REQUIRE : SIGN(C**2 - S**2) = SIGN(XXAV - YYAV)
195 Double_t sinrot, cosrot ;
196 if ( xxav <= yyav ) {
205 //-> REQUIRE : SIGN(S) = SIGN(XYAV) * SIGN(C) (ASSUMING SIGN(C) > 0)
207 if ( xyav < 0.0 ) sinrot = - sinrot ;
209 //--> WE NOW HAVE THE SMALLEST ANGLE THAT GUARANTEES <X**2> > <Y**2>
210 //--> TO GET THE SIGN OF THE CHARGE RIGHT, THE NEW X-AXIS MUST POINT
211 //--> OUTWARD FROM THE ORGIN. WE ARE FREE TO CHANGE SIGNS OF BOTH
212 //--> COSROT AND SINROT SIMULTANEOUSLY TO ACCOMPLISH THIS.
214 //--> CHOOSE SIGN OF C WISELY TO BE ABLE TO GET THE SIGN OF THE CHARGE
216 if ( cosrot*xav+sinrot*yav < 0.0 ) {
221 //-> NOW GET <R**2> AND RSCALE= SQRT(<R**2>)
223 Double_t rrav = xxav + yyav ;
224 Double_t rscale = sqrt(rrav) ;
229 Double_t xrrav = 0.0 ;
230 Double_t yrrav = 0.0 ;
231 Double_t rrrrav = 0.0 ;
233 Double_t xixi, yiyi, riri, wiriri, xold, yold ;
235 //for (hit_counter=0; hit_counter<numOfHits; hit_counter++)
236 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit())
238 //AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)hits->At(hit_counter);
239 AliHLTTPCConfMapPoint* cHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
241 xold = cHit->GetX() - xav ;
242 yold = cHit->GetY() - yav ;
244 //--> ROTATE SO THAT <XY> = 0 & DIVIDE BY RSCALE SO THAT <R**2> = 1
246 xi = ( cosrot * xold + sinrot * yold ) / rscale ;
247 yi = ( -sinrot * xold + cosrot * yold ) / rscale ;
252 wiriri = cHit->GetXYWeight() * riri ;
254 xyav += cHit->GetXYWeight() * xi * yi ;
255 xxav += cHit->GetXYWeight() * xixi ;
256 yyav += cHit->GetXYWeight() * yiyi ;
258 xrrav += wiriri * xi ;
259 yrrav += wiriri * yi ;
260 rrrrav += wiriri * riri ;
263 // Include vertex if required
265 if (fTrack->ComesFromMainVertex() == true)
267 xold = fVertex->GetX() - xav ;
268 yold = fVertex->GetY() - yav ;
270 //--> ROTATE SO THAT <XY> = 0 & DIVIDE BY RSCALE SO THAT <R**2> = 1
272 xi = ( cosrot * xold + sinrot * yold ) / rscale ;
273 yi = ( -sinrot * xold + cosrot * yold ) / rscale ;
278 wiriri = fVertex->GetXYWeight() * riri ;
280 xyav += fVertex->GetXYWeight() * xi * yi ;
281 xxav += fVertex->GetXYWeight() * xixi ;
282 yyav += fVertex->GetXYWeight() * yiyi ;
284 xrrav += wiriri * xi ;
285 yrrav += wiriri * yi ;
286 rrrrav += wiriri * riri ;
291 //--> DIVIDE BY WSUM TO MAKE AVERAGES
295 xrrav = xrrav / wsum ;
296 yrrav = yrrav / wsum ;
297 rrrrav = rrrrav / wsum ;
300 const Int_t ntry = 5 ;
302 //--> USE THESE TO GET THE COEFFICIENTS OF THE 4-TH ORDER POLYNIMIAL
303 //--> DON'T PANIC - THE THIRD ORDER TERM IS ZERO !
305 Double_t xrrxrr = xrrav * xrrav ;
306 Double_t yrryrr = yrrav * yrrav ;
307 Double_t rrrrm1 = rrrrav - 1.0 ;
308 Double_t xxyy = xxav * yyav ;
310 Double_t c0 = rrrrm1*xxyy - xrrxrr*yyav - yrryrr*xxav ;
311 Double_t c1 = - rrrrm1 + xrrxrr + yrryrr - 4.0*xxyy ;
312 Double_t c2 = 4.0 + rrrrm1 - 4.0*xxyy ;
313 Double_t c4 = - 4.0 ;
315 //--> COEFFICIENTS OF THE DERIVATIVE - USED IN NEWTON-RAPHSON ITERATIONS
317 Double_t c2d = 2.0 * c2 ;
318 Double_t c4d = 4.0 * c4 ;
320 //--> 0'TH VALUE OF LAMDA - LINEAR INTERPOLATION BETWEEN P(0) & P(YYAV)
322 // LAMDA = YYAV * C0 / (C0 + YRRSQ * (XXAV-YYAV))
323 Double_t lamda = 0.0 ;
324 Double_t dlamda = 0.0 ;
326 Double_t chiscl = wsum * rscale * rscale ;
327 Double_t dlamax = 0.001 / chiscl ;
330 for ( int itry = 1 ; itry <= ntry ; itry++ ) {
331 p = c0 + lamda * (c1 + lamda * (c2 + lamda * lamda * c4 )) ;
332 pd = (c1 + lamda * (c2d + lamda * lamda * c4d)) ;
334 lamda = lamda + dlamda ;
335 if (fabs(dlamda)< dlamax) break ;
338 Double_t chi2 = (Double_t)(chiscl * lamda) ;
340 fTrack->SetChiSq1(chi2);
341 // Double_t dchisq = chiscl * dlamda ;
343 //--> NOW CALCULATE THE MATRIX ELEMENTS FOR ALPHA, BETA & KAPPA
345 Double_t h11 = xxav - lamda ;
346 Double_t h14 = xrrav ;
347 Double_t h22 = yyav - lamda ;
348 Double_t h24 = yrrav ;
349 Double_t h34 = 1.0 + 2.0*lamda ;
350 if ( h11 == 0.0 || h22 == 0.0 ){
351 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitCircle","TrackFit")<<AliHLTTPCLog::kDec<<
352 "Problems fitting circle"<<ENDLOG;
355 Double_t rootsq = (h14*h14)/(h11*h11) + 4.0*h34 ;
357 Double_t ratio, kappa, beta ;
358 if ( fabs(h22) > fabs(h24) ) {
360 rootsq = ratio * ratio + rootsq ;
361 kappa = 1.0 / sqrt(rootsq) ;
362 beta = - ratio * kappa ;
366 rootsq = 1.0 + ratio * ratio * rootsq ;
367 beta = 1.0 / sqrt(rootsq) ;
368 if ( h24 > 0 ) beta = - beta ;
369 kappa = -ratio * beta ;
371 Double_t alpha = - (h14/h11) * kappa ;
373 //--> transform these into the lab coordinate system
374 //--> first get kappa and back to real dimensions
376 Double_t kappa1 = kappa / rscale ;
377 Double_t dbro = 0.5 / kappa1 ;
379 //--> next rotate alpha and beta and scale
381 Double_t alphar = (cosrot * alpha - sinrot * beta)* dbro ;
382 Double_t betar = (sinrot * alpha + cosrot * beta)* dbro ;
384 //--> then translate by (xav,yav)
386 Double_t acent = (double)(xav - alphar) ;
387 Double_t bcent = (double)(yav - betar ) ;
388 Double_t radius = (double)dbro ;
392 Int_t q = ( ( yrrav < 0 ) ? 1 : -1 ) ;
394 fTrack->SetCharge(q);
397 //Set the first point on the track to the space point coordinates of the innermost track
398 //This will be updated to lie on the fit later on (AliHLTTPCTrack::UpdateToFirstPoint).
399 Double_t x0,y0,psi,pt ;
400 AliHLTTPCConfMapPoint *lHit = (AliHLTTPCConfMapPoint*)fTrack->GetLastHit();
403 fTrack->SetFirstPoint(x0,y0,0); //Z-value is set in FitLine
405 psi = (Double_t)atan2(bcent-y0,acent-x0) ;
406 psi = psi + q * AliHLTTPCTransform::PiHalf();
407 if ( psi < 0 ) psi = psi + AliHLTTPCTransform::TwoPi();
408 pt = (Double_t)(AliHLTTPCTransform::GetBFieldValue() * radius ) ;
410 //Update the track parameters with the parameters from this fit:
413 fTrack->SetRadius(radius);
414 fTrack->SetCenterX(acent);
415 fTrack->SetCenterY(bcent);
418 // Get errors from fast fit
420 //if ( getPara()->getErrors ) getErrorsCircleFit ( acent, bcent, radius ) ;
426 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
427 // Fit Line in s-z plane
428 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
429 Int_t AliHLTTPCConfMapFit::FitLine ( )
440 //find sum , sums ,sumz, sumss
443 Double_t radius = (Double_t)(fTrack->GetPt() / AliHLTTPCTransform::GetBFieldValue() ) ;
445 //TObjArray *hits = fTrack->GetHits();
446 //Int_t numOfHits = fTrack->GetNumberOfPoints();
448 if (0)// fTrack->ComesFromMainVertex() == true )
450 dx = ((AliHLTTPCConfMapPoint*)fTrack->GetFirstHit())->GetX() - fVertex->GetX();
451 dy = ((AliHLTTPCConfMapPoint*)fTrack->GetFirstHit())->GetY() - fVertex->GetY() ;
455 dx = ((AliHLTTPCConfMapPoint *)fTrack->GetFirstHit())->GetX() - ((AliHLTTPCConfMapPoint *)fTrack->GetLastHit())->GetX() ;
456 dy = ((AliHLTTPCConfMapPoint *)fTrack->GetFirstHit())->GetY() - ((AliHLTTPCConfMapPoint *)fTrack->GetLastHit())->GetY() ;
457 //dx = ((AliHLTTPCConfMapPoint *)hits->First())->GetX() - ((AliHLTTPCConfMapPoint *)hits->Last())->GetX() ;
458 //dy = ((AliHLTTPCConfMapPoint *)hits->First())->GetY() - ((AliHLTTPCConfMapPoint *)hits->Last())->GetY() ;
461 Double_t localPsi = 0.5F * sqrt ( dx*dx + dy*dy ) / radius ;
464 if ( fabs(localPsi) < 1. )
466 totalS = 2.0 * radius * asin ( localPsi ) ;
470 totalS = 2.0 * radius * AliHLTTPCTransform::Pi() ;
473 AliHLTTPCConfMapPoint *previousHit = NULL;
475 // FtfBaseHit *previousHit = 0 ;
477 //for ( startLoop() ; done() ; nextHit() ) {
480 // for(hit_counter=0; hit_counter<numOfHits; hit_counter++)
481 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit())
483 // AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)hits->At(hit_counter);
484 AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
485 // if ( GetCurrentHit() != GetFirstHit() )
486 if(cHit != fTrack->GetFirstHit())// hits->First())
488 dx = cHit->GetX() - previousHit->GetX() ;
489 dy = cHit->GetY() - previousHit->GetY() ;
490 dpsi = 0.5 * (Double_t)sqrt ( dx*dx + dy*dy ) / radius ;
491 fTrack->SetPsierr(dpsi);
492 s = previousHit->GetS() - 2.0 * radius * (Double_t)asin ( dpsi ) ;
497 // cHit->s = totalS ;
499 sum += cHit->GetZWeight() ;
500 ss += cHit->GetZWeight() * cHit->GetS() ;
501 sz += cHit->GetZWeight() * cHit->GetZ() ;
502 sss += cHit->GetZWeight() * cHit->GetS() * cHit->GetS() ;
503 ssz += cHit->GetZWeight() * cHit->GetS() * cHit->GetZ() ;
507 Double_t chi2,det = sum * sss - ss * ss;
508 if ( fabs(det) < 1e-20)
511 fTrack->SetChiSq2(chi2);
515 //Compute the best fitted parameters A,B
516 Double_t tanl,z0,dtanl,dz0;
518 tanl = (Double_t)((sum * ssz - ss * sz ) / det );
519 z0 = (Double_t)((sz * sss - ssz * ss ) / det );
521 fTrack->SetTgl(tanl);
524 // calculate chi-square
529 //for(hit_counter=0; hit_counter<numOfHits; hit_counter++)
530 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit())
532 //AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)hits->At(hit_counter);
533 AliHLTTPCConfMapPoint *cHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
534 r1 = cHit->GetZ() - tanl * cHit->GetS() - z0 ;
535 chi2 += (Double_t) ( (Double_t)cHit->GetZWeight() * (r1 * r1) );
537 fTrack->SetChiSq2(chi2);
539 // calculate estimated variance
540 // varsq=chi/(double(n)-2.)
541 // calculate covariance matrix
542 // siga=sqrt(varsq*sxx/det)
543 // sigb=sqrt(varsq*sum/det)
545 dtanl = (Double_t) ( sum / det );
546 dz0 = (Double_t) ( sss / det );
548 fTrack->SetTglerr(dtanl);
549 fTrack->SetZ0err(dz0);
555 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
556 // Straight Line Fit in x-y plane
557 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
558 Int_t AliHLTTPCConfMapFit::FitLineXY ( ){
559 // -----------------------------------------------------------------------------
560 // Implementation after Numerical Recipes in C, 2nd Edtion, chapter 15.2, p. 661
562 // and Data Analysis for Physical Science Students, Luis Lyons, chapter 2.4 p.51
563 // with y = a' + bx' , x' = x - <x>
564 // -----------------------------------------------------------------------------
569 Double_t sPrime = 0.;
570 Double_t sxPrime = 0.;
571 Double_t sxxPrime = 0.;
572 Double_t syPrime = 0.;
573 Double_t sxyPrime = 0.;
577 Int_t numOfHits = fTrack->GetNumberOfPoints();
581 // - Loop over hits calculating average : xav
582 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
584 AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
585 // ** maybe not necessary, already done in ConfMapPoint
586 currentHit->SetXYWeight( 1./ (Double_t)(currentHit->GetXerr()*currentHit->GetXerr() + currentHit->GetYerr()*currentHit->GetYerr()) );
588 s += currentHit->GetXYWeight();
589 sx += currentHit->GetXYWeight() * currentHit->GetX();
593 LOG(AliHLTTPCLog::kError,"AliHLTTPCConfMapFit::FitLineXY","TrackFit") << "Mismatch of hits. Counter: "<<co<<" nHits: "<<numOfHits<<ENDLOG;
595 Double_t xav = (Double_t)sx / s;
597 // Calculate weighted means
598 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
599 AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
601 Double_t xPrime = currentHit->GetX() - xav;
602 sPrime += currentHit->GetXYWeight();
603 sxPrime += currentHit->GetXYWeight() * xPrime;
604 sxxPrime += currentHit->GetXYWeight() * xPrime * xPrime;
605 syPrime += currentHit->GetXYWeight() * currentHit->GetY();
606 sxyPrime += currentHit->GetXYWeight() * xPrime * currentHit->GetY();
609 Double_t det = sPrime*sxxPrime + sxPrime*sxPrime;
611 if (fabs(det) < 1e-20) {
612 LOG(AliHLTTPCLog::kDebug,"AliHLTTPCConfMapFit::FitLineXY","TrackFit") << "Determinant == 0" << ENDLOG;
614 fTrack->SetChiSq1(chi2);
618 Double_t b = (Double_t)(sPrime*sxyPrime - sxPrime*syPrime) / det; // line parameter b
619 Double_t aPrime = (Double_t)(sxxPrime*syPrime - sxPrime*sxyPrime) / det; // line parameter a
621 Double_t sigma2b = (Double_t)1. / sxxPrime;
622 //-- Double_t sigma2aprime = (Double_t)1. /sPrime;
624 // Get gradient angle psi of line in xy plane
625 Double_t psi = (Double_t) atan(b) ;
628 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
629 AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
630 Double_t tempchi = currentHit->GetY() - aPrime - b*(currentHit->GetX() - xav);
631 chi2 += tempchi*tempchi*currentHit->GetXYWeight() ;
634 Double_t a = aPrime - b*xav;
637 // Set TrackParameter
638 fTrack->SetChiSq1(chi2);
640 fTrack->SetPsierr(sigma2b);
641 fTrack->SetCenterX(0.); // Set to point on the track (for UpdateToFirstPoint)
642 fTrack->SetCenterY(a); // Set to point on the track (for UpdateToFirstPoint)
644 //Set the first point on the track to the space point coordinates of the innermost track
645 //This will be updated to lie on the fit later on (AliHLTTPCTrack::UpdateToFirstPoint).
646 AliHLTTPCConfMapPoint *lastHit = (AliHLTTPCConfMapPoint*)fTrack->GetLastHit();
647 Double_t x0 = lastHit->GetX();
648 Double_t y0 = lastHit->GetY();
649 fTrack->SetFirstPoint(x0,y0,0); //Z-value is set in FitLineSZ
653 fTrack->SetRadius(-1.);
654 fTrack->SetCharge(1);
662 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
663 // Straight Line Fit in s-z plane
664 //+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
665 Int_t AliHLTTPCConfMapFit::FitLineSZ ( ){
666 // -----------------------------------------------------------------------------
667 // Implementation after Numerical Recipes in C, 2nd Edtion, chapter 15.2, p. 661
669 // and Data Analysis for Physical Science Students, Luis Lyons, chapter 2.4 p.51
670 // with z = a' + bs' , s' = s - <s>
671 // -----------------------------------------------------------------------------
676 Double_t sPrime = 0.;
677 Double_t ssPrime = 0.;
678 Double_t sssPrime = 0.;
679 Double_t szPrime = 0.;
680 Double_t sszPrime = 0.;
684 // Matthias 16.10.2007
685 // what's that!!! local variables 's' and 'S'
686 // change Double_t s = 0.; -> slength
687 Double_t slength = 0.;
689 AliHLTTPCConfMapPoint *previousHit = NULL;
691 // - Loop over hits calculating length in xy-plane: s
692 // - Loop over hits calculating average : sav
693 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
694 AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
695 if(currentHit != fTrack->GetFirstHit()) {
696 Double_t dx = currentHit->GetX() - previousHit->GetX() ;
697 Double_t dy = currentHit->GetY() - previousHit->GetY() ;
698 slength = previousHit->GetS() - (Double_t)sqrt ( dx*dx + dy*dy );
701 Double_t dx = ((AliHLTTPCConfMapPoint *)fTrack->GetFirstHit())->GetX() - ((AliHLTTPCConfMapPoint *)fTrack->GetLastHit())->GetX();
702 Double_t dy = ((AliHLTTPCConfMapPoint *)fTrack->GetFirstHit())->GetY() - ((AliHLTTPCConfMapPoint *)fTrack->GetLastHit())->GetY();
703 slength = (Double_t)sqrt ( dx*dx + dy*dy );
706 currentHit->SetS(slength);
708 S += currentHit->GetZWeight();
709 Ss += currentHit->GetZWeight() * currentHit->GetS();
712 Double_t sav = (Double_t)Ss / S;
714 // Calculate weighted means
715 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
716 AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
718 Double_t sPrime = currentHit->GetS() - sav;
719 sPrime += currentHit->GetZWeight();
720 ssPrime += currentHit->GetZWeight() * sPrime;
721 sssPrime += currentHit->GetZWeight() * sPrime * sPrime;
722 szPrime += currentHit->GetZWeight() * currentHit->GetZ();
723 sszPrime += currentHit->GetZWeight() * sPrime * currentHit->GetZ();
726 Double_t det = sPrime*sssPrime + ssPrime*ssPrime;
728 if (fabs(det) < 1e-20) {
729 LOG(AliHLTTPCLog::kDebug,"AliHLTTPCConfMapFit::FitLineSZ","TrackFit") << "Determinant == 0" << ENDLOG;
731 fTrack->SetChiSq2(chi2);
735 Double_t b = (Double_t)(sPrime*sszPrime - ssPrime*szPrime) / det; // line parameter b
736 Double_t aPrime = (Double_t)(sssPrime*szPrime - ssPrime*sszPrime) / det; // line parameter a
738 Double_t a = aPrime - b*sav;
740 Double_t sigma2b = (Double_t) 1. / sssPrime;
741 Double_t sigma2aprime = (Double_t) 1. /sPrime;
743 Double_t sigma2a = sigma2aprime + sav*sav * sigma2b*sigma2b;
746 for(fTrack->StartLoop(); fTrack->LoopDone(); fTrack->GetNextHit()) {
747 AliHLTTPCConfMapPoint *currentHit = (AliHLTTPCConfMapPoint*)fTrack->GetCurrentHit();
748 Double_t tempchi = currentHit->GetZ() - aPrime - b*(currentHit->GetS() - sav);
749 chi2 += tempchi*tempchi*currentHit->GetZWeight() ;
752 // Set TrackParameter
753 fTrack->SetChiSq2(chi2);
756 fTrack->SetTglerr(sigma2b);
757 // fTrack->SetZ0err(sigma2aprime); // maybe subject to check
758 fTrack->SetZ0err(sigma2a); // maybe subject to check