4 /* Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
5 * See cxx source for full Copyright notice */
8 //-------------------------------------------------------------------------
11 // Origin: Marian Ivanov marian.ivanov@cern.ch
12 //-------------------------------------------------------------------------
20 class AliExternalTrackParam;
22 class AliHelix : public TObject {
25 AliHelix(const AliHelix &t);
26 AliHelix(const AliKalmanTrack &t);
27 AliHelix(const AliExternalTrackParam &t);
28 AliHelix(Double_t x[3], Double_t p[3], Double_t charge=1, Double_t conversion=0.);
29 virtual ~AliHelix(){};
30 inline void Evaluate(Double_t t, Double_t r[3]);
31 void Evaluate(Double_t t, Double_t r[3], //radius vector
32 Double_t g[3], //first defivatives
33 Double_t gg[3]); //second derivatives
34 void GetMomentum(Double_t phase, Double_t p[4], Double_t conversion=0.); // return momentum
35 void GetAngle(Double_t t1, AliHelix &h, Double_t t2, Double_t angle[3]);
36 inline Double_t GetHelixR(Double_t phase=0);
37 inline Double_t GetHelixZ(Double_t phase=0);
39 Double_t GetPhase(Double_t x0, Double_t y0); //return phase for nearest point
40 Double_t GetPhaseZ(Double_t z0); // return phase for given z
41 Int_t GetPhase(Double_t r0, Double_t t[2]); //return phase for the nearest point
42 Int_t GetRPHIintersections(AliHelix &h, Double_t phase[2][2], Double_t ri[2], Double_t cut=3.);
43 Int_t LinearDCA(AliHelix &h, Double_t &t1, Double_t &t2,
44 Double_t &R, Double_t &dist);
46 Int_t ParabolicDCA(AliHelix&h, //helixes
47 Double_t &t1, Double_t &t2,
48 Double_t &R, Double_t &dist, Int_t iter=1);
50 Double_t fHelix[9]; //helix parameters
52 ClassDef(AliHelix,1) // AliHelix
55 void AliHelix::Evaluate(Double_t t, Double_t r[3]){
57 // calculate poitition at given phase t
58 Double_t phase=fHelix[4]*t+fHelix[2];
59 r[0] = fHelix[5] + TMath::Sin(phase)/fHelix[4];
60 r[1] = fHelix[0] - TMath::Cos(phase)/fHelix[4];
61 r[2] = fHelix[1] + fHelix[3]*t;
64 inline Double_t AliHelix::GetHelixR(Double_t phase)
68 return TMath::Sqrt(x[0]*x[0]+x[1]*x[1]);
71 inline Double_t AliHelix::GetHelixZ(Double_t phase)