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998b831f | 1 | #ifndef AliRICHHelix_h |
2 | #define AliRICHHelix_h | |
3 | ||
4 | #include <TObject.h> | |
5 | #include <TVector3.h> | |
6 | #include "AliRICHParam.h" | |
7 | #include "AliRICHChamber.h" | |
8 | ||
9 | class AliRICHHelix: public TObject | |
10 | { | |
11 | public: | |
12 | AliRICHHelix() {;} | |
13 | AliRICHHelix(TVector3 x0,TVector3 p0,Int_t q,Double_t b=0.4) {fX0=x0;fP0=p0;fQ=q;fBz=b;} //takes position and momentum at parametrised point | |
14 | virtual ~AliRICHHelix() {;} | |
15 | inline void Propagate(Double_t lenght); | |
16 | Bool_t Intersection(TVector3 plane) {return Intersection(plane,plane.Unit());} // special plane given by point only | |
17 | inline Bool_t Intersection(TVector3 planePoint,TVector3 planeNorm); //intersection with plane given by point and normal vector | |
18 | inline Int_t RichIntersect(AliRICHParam *pParam); | |
19 | TVector3 X()const {return fX;} | |
20 | TVector3 P()const {return fP;} | |
21 | TVector3 X0()const {return fX0;} | |
22 | TVector3 P0()const {return fP0;} | |
23 | TVector2 PosPc() const {return fPosPc;} //returns position of intersection with PC | |
24 | TVector2 PosRad()const {return fPosRad;} //returns position of intersection with radiator | |
25 | TVector3 Ploc()const {return fPloc;} //returns momentum at the position of intersection with radiator | |
26 | ||
27 | void Print(Option_t *sOption)const; //virtual interface from TObject | |
28 | protected: | |
29 | TVector3 fX0; //helix position in parametrised point, cm in MRS | |
30 | TVector3 fP0; //helix momentum in parametrised point, GeV/c in MRS | |
31 | TVector3 fX; //helix position in point of interest, cm in MRS | |
32 | TVector3 fP; //helix momentum in point of interest, GeV/c in MRS | |
33 | Double_t fLength; //helix length in point of interest | |
34 | Int_t fQ; //sign of track charge (value not provided by current ESD) | |
35 | Double_t fBz; //magnetic field along z value in Tesla under assumption of uniformity | |
36 | TVector2 fPosPc; //position on PC in local system | |
37 | TVector2 fPosRad; //position on radiator in local system | |
38 | TVector3 fPloc; //momentum in local system | |
39 | ClassDef(AliRICHHelix,0) //General helix | |
40 | };//class AliRICHHelix | |
41 | //__________________________________________________________________________________________________ | |
42 | void AliRICHHelix::Propagate(Double_t length) | |
43 | { | |
44 | // Propogates the helix to the position of interest defined by helix length s | |
45 | // Assumes uniform magnetic field along z direction. | |
46 | const Double_t c = 0.00299792458;//this value provides that coordinates are in cm momentum in GeV/c | |
47 | Double_t a = -c*fBz*fQ; | |
48 | ||
49 | Double_t rho = a/fP0.Mag(); | |
50 | fX.SetX( fX0.X()+fP0.X()*TMath::Sin(rho*length)/a-fP0.Y()*(1-TMath::Cos(rho*length))/a ); | |
51 | fX.SetY( fX0.Y()+fP0.Y()*TMath::Sin(rho*length)/a+fP0.X()*(1-TMath::Cos(rho*length))/a ); | |
52 | fX.SetZ( fX0.Z()+fP0.Z()*length/fP0.Mag() ); | |
53 | fP.SetX( fP0.X()*TMath::Cos(rho*length)-fP0.Y()*TMath::Sin(rho*length) ); | |
54 | fP.SetY( fP0.Y()*TMath::Cos(rho*length)+fP0.X()*TMath::Sin(rho*length) ); | |
55 | fP.SetZ( fP0.Z() ); | |
56 | fLength=length; | |
57 | } | |
58 | //__________________________________________________________________________________________________ | |
59 | Bool_t AliRICHHelix::Intersection(TVector3 planePoint,TVector3 planeNorm) | |
60 | { | |
61 | // Finds point of intersection (if exists) of the helix to the plane given by point and normal vector. | |
62 | // Returns kTrue if helix intersects the plane, kFALSE otherwise. | |
63 | // Stores result in current helix fields fX and fP. | |
64 | ||
65 | Double_t s=(planePoint-fX0)*planeNorm,dist=99999,distPrev=dist; | |
66 | ||
67 | while(TMath::Abs(dist)>0.0001){ | |
68 | Propagate(s); //calculates helix at the distance s from x0 ALONG the helix | |
69 | dist=(fX-planePoint)*planeNorm; //distance between current helix position and plane | |
70 | if(TMath::Abs(dist) > TMath::Abs(distPrev)) { return kFALSE;} | |
71 | distPrev=dist; | |
72 | s-=dist; | |
73 | } | |
74 | return kTRUE; | |
75 | } | |
76 | //__________________________________________________________________________________________________ | |
77 | Int_t AliRICHHelix::RichIntersect(AliRICHParam *pParam) | |
78 | { | |
79 | // Searchs for intersection of this helix with all RICH chambers, returns chamber number or 0 if no intersection | |
80 | // On exit fPosRad contain position of intersection in Local System with radiator | |
81 | // fPosPc contains the same for photocathode | |
82 | for(Int_t iChamberN=1;iChamberN<=kNchambers;iChamberN++){//chamber loop | |
83 | if(Intersection(pParam->C(iChamberN)->Rad())){//there is intersection with radiator plane | |
84 | fPosRad=pParam->C(iChamberN)->Mrs2Rad(fX);//position on radiator plane | |
85 | if(pParam->IsAccepted(fPosRad)){//intersection within radiator (even if in dead zone) | |
86 | if(Intersection(pParam->C(iChamberN)->Pc())){//there is intersection with photocathode | |
87 | fPosPc=pParam->C(iChamberN)->Mrs2Pc(fX);//position on photcathode plane | |
88 | if(pParam->IsAccepted(fPosPc)){//intersection within pc (even if in dead zone) | |
89 | fPloc=pParam->C(iChamberN)->PMrs2Loc(fP); | |
90 | return iChamberN; | |
91 | }//if inside PC | |
92 | }//if for PC | |
93 | }//if inside radiator | |
94 | }//if for radiator | |
95 | }//chamber loop | |
96 | return 0; | |
97 | } | |
98 | //__________________________________________________________________________________________________ | |
99 | #endif |