From 4dcdc747c237bc1bed58af4e4d78eb7c00a804be Mon Sep 17 00:00:00 2001 From: cvetan Date: Thu, 5 Jul 2007 11:23:31 +0000 Subject: [PATCH] New method to calculate correctly the track extrapolation on a reference frame. Or, in other words, the method finds the point of the closest approach between two space-points --- STEER/AliTrackPointArray.cxx | 59 ++++++++++++++++++++++++++++++++++++ STEER/AliTrackPointArray.h | 1 + 2 files changed, 60 insertions(+) diff --git a/STEER/AliTrackPointArray.cxx b/STEER/AliTrackPointArray.cxx index 92b2b15db0f..3b843d7f29f 100644 --- a/STEER/AliTrackPointArray.cxx +++ b/STEER/AliTrackPointArray.cxx @@ -23,6 +23,7 @@ ////////////////////////////////////////////////////////////////////////////// #include +#include #include #include "AliTrackPointArray.h" @@ -299,6 +300,64 @@ Float_t AliTrackPoint::GetResidual(const AliTrackPoint &p, Bool_t weighted) cons return res; } +//_____________________________________________________________________________ +Bool_t AliTrackPoint::GetPCA(const AliTrackPoint &p, AliTrackPoint &out) const +{ + // + // Get the intersection point between this point and + // the point "p" belongs to. + // The result is stored as a point 'out' + // return kFALSE in case of failure. + out.SetXYZ(0,0,0); + + TMatrixD t(3,1); + t(0,0)=GetX(); + t(1,0)=GetY(); + t(2,0)=GetZ(); + + TMatrixDSym tC(3); + { + const Float_t *cv=GetCov(); + tC(0,0)=cv[0]; tC(0,1)=cv[1]; tC(0,2)=cv[2]; + tC(1,0)=cv[1]; tC(1,1)=cv[3]; tC(1,2)=cv[4]; + tC(2,0)=cv[2]; tC(2,1)=cv[4]; tC(2,2)=cv[5]; + } + + TMatrixD m(3,1); + m(0,0)=p.GetX(); + m(1,0)=p.GetY(); + m(2,0)=p.GetZ(); + + TMatrixDSym mC(3); + { + const Float_t *cv=p.GetCov(); + mC(0,0)=cv[0]; mC(0,1)=cv[1]; mC(0,2)=cv[2]; + mC(1,0)=cv[1]; mC(1,1)=cv[3]; mC(1,2)=cv[4]; + mC(2,0)=cv[2]; mC(2,1)=cv[4]; mC(2,2)=cv[5]; + } + + TMatrixDSym tmW(tC); + tmW+=mC; + tmW.Invert(); + if (!tmW.IsValid()) return kFALSE; + + TMatrixD mW(tC,TMatrixD::kMult,tmW); + TMatrixD tW(mC,TMatrixD::kMult,tmW); + + TMatrixD mi(mW,TMatrixD::kMult,m); + TMatrixD ti(tW,TMatrixD::kMult,t); + ti+=mi; + + TMatrixD iC(tC,TMatrixD::kMult,tmW); + iC*=mC; + + out.SetXYZ(ti(0,0),ti(1,0),ti(2,0)); + UShort_t id=p.GetVolumeID(); + out.SetVolumeID(id); + + return kTRUE; +} + //______________________________________________________________________________ Float_t AliTrackPoint::GetAngle() const { diff --git a/STEER/AliTrackPointArray.h b/STEER/AliTrackPointArray.h index b7c6aa48145..6e604f35229 100644 --- a/STEER/AliTrackPointArray.h +++ b/STEER/AliTrackPointArray.h @@ -38,6 +38,7 @@ class AliTrackPoint : public TObject { UShort_t GetVolumeID() const { return fVolumeID; } Float_t GetResidual(const AliTrackPoint &p, Bool_t weighted = kFALSE) const; + Bool_t GetPCA(const AliTrackPoint &p, AliTrackPoint &out) const; Float_t GetAngle() const; AliTrackPoint& Rotate(Float_t alpha) const; -- 2.27.0