class TGeoHelix: public TObject
TGeoHelix - class representing a helix curve A helix is a curve defined by the following equations: x = (1/c) * COS(q*phi) y = (1/c) * SIN(q*phi) z = s * alfa where: c = 1/Rxy - curvature in XY plane phi - phi angle S = 2*PI*s - vertical separation between helix loops q = +/- 1 - (+)=left-handed, (-)=right-handed In particular, a helix describes the trajectory of a charged particle in magnetic field. In such case, the helix is right-handed for negative particle charge. To define a helix, one must define: - the curvature - positive defined - the Z step made after one full turn of the helix - the particle charge sign - the initial particle position and direction (force normalization to unit) - the magnetic field direction A helix provides: - propagation to a given Z position (in global frame) Double_t *point = TGeoHelix::PropagateToZ(Double_t z); - propagation to an arbitrary plane, returning also the new point - propagation in a geometry until the next crossed surface - computation of the total track length along a helix
Function Members (Methods)
public:
| TGeoHelix() | |
| TGeoHelix(Double_t curvature, Double_t step, Int_t charge = 1) | |
| virtual | ~TGeoHelix() |
| void | TObject::AbstractMethod(const char* method) const |
| virtual void | TObject::AppendPad(Option_t* option = "") |
| virtual void | TObject::Browse(TBrowser* b) |
| static TClass* | Class() |
| virtual const char* | TObject::ClassName() const |
| virtual void | TObject::Clear(Option_t* = "") |
| virtual TObject* | TObject::Clone(const char* newname = "") const |
| virtual Int_t | TObject::Compare(const TObject* obj) const |
| Double_t | ComputeSafeStep(Double_t epsil = 1E-6) const |
| virtual void | TObject::Copy(TObject& object) const |
| virtual void | TObject::Delete(Option_t* option = "")MENU |
| virtual Int_t | TObject::DistancetoPrimitive(Int_t px, Int_t py) |
| virtual void | TObject::Draw(Option_t* option = "") |
| virtual void | TObject::DrawClass() constMENU |
| virtual TObject* | TObject::DrawClone(Option_t* option = "") constMENU |
| virtual void | TObject::Dump() constMENU |
| virtual void | TObject::Error(const char* method, const char* msgfmt) const |
| virtual void | TObject::Execute(const char* method, const char* params, Int_t* error = 0) |
| virtual void | TObject::Execute(TMethod* method, TObjArray* params, Int_t* error = 0) |
| virtual void | TObject::ExecuteEvent(Int_t event, Int_t px, Int_t py) |
| virtual void | TObject::Fatal(const char* method, const char* msgfmt) const |
| virtual TObject* | TObject::FindObject(const char* name) const |
| virtual TObject* | TObject::FindObject(const TObject* obj) const |
| const Double_t* | GetCurrentDirection() const |
| const Double_t* | GetCurrentPoint() const |
| virtual Option_t* | TObject::GetDrawOption() const |
| static Long_t | TObject::GetDtorOnly() |
| virtual const char* | TObject::GetIconName() const |
| virtual const char* | TObject::GetName() const |
| virtual char* | TObject::GetObjectInfo(Int_t px, Int_t py) const |
| static Bool_t | TObject::GetObjectStat() |
| virtual Option_t* | TObject::GetOption() const |
| Double_t | GetStep() const |
| virtual const char* | TObject::GetTitle() const |
| Double_t | GetTotalCurvature() const |
| virtual UInt_t | TObject::GetUniqueID() const |
| Double_t | GetXYcurvature() const |
| virtual Bool_t | TObject::HandleTimer(TTimer* timer) |
| virtual ULong_t | TObject::Hash() const |
| virtual void | TObject::Info(const char* method, const char* msgfmt) const |
| virtual Bool_t | TObject::InheritsFrom(const char* classname) const |
| virtual Bool_t | TObject::InheritsFrom(const TClass* cl) const |
| void | InitDirection(Double_t* dir, Bool_t is_normalized = kTRUE) |
| void | InitDirection(Double_t dirx, Double_t diry, Double_t dirz, Bool_t is_normalized = kTRUE) |
| void | InitPoint(Double_t* point) |
| void | InitPoint(Double_t x0, Double_t y0, Double_t z0) |
| virtual void | TObject::Inspect() constMENU |
| void | TObject::InvertBit(UInt_t f) |
| virtual TClass* | IsA() const |
| virtual Bool_t | TObject::IsEqual(const TObject* obj) const |
| virtual Bool_t | TObject::IsFolder() const |
| Bool_t | TObject::IsOnHeap() const |
| Bool_t | IsRightHanded() const |
| virtual Bool_t | TObject::IsSortable() const |
| Bool_t | TObject::IsZombie() const |
| virtual void | TObject::ls(Option_t* option = "") const |
| void | TObject::MayNotUse(const char* method) const |
| virtual Bool_t | TObject::Notify() |
| void | TObject::Obsolete(const char* method, const char* asOfVers, const char* removedFromVers) const |
| static void | TObject::operator delete(void* ptr) |
| static void | TObject::operator delete(void* ptr, void* vp) |
| static void | TObject::operator delete[](void* ptr) |
| static void | TObject::operator delete[](void* ptr, void* vp) |
| void* | TObject::operator new(size_t sz) |
| void* | TObject::operator new(size_t sz, void* vp) |
| void* | TObject::operator new[](size_t sz) |
| void* | TObject::operator new[](size_t sz, void* vp) |
| virtual void | TObject::Paint(Option_t* option = "") |
| virtual void | TObject::Pop() |
| virtual void | TObject::Print(Option_t* option = "") const |
| virtual Int_t | TObject::Read(const char* name) |
| virtual void | TObject::RecursiveRemove(TObject* obj) |
| void | TObject::ResetBit(UInt_t f) |
| void | ResetStep() |
| virtual void | TObject::SaveAs(const char* filename = "", Option_t* option = "") constMENU |
| virtual void | TObject::SavePrimitive(ostream& out, Option_t* option = "") |
| void | TObject::SetBit(UInt_t f) |
| void | TObject::SetBit(UInt_t f, Bool_t set) |
| void | SetCharge(Int_t charge) |
| virtual void | TObject::SetDrawOption(Option_t* option = "")MENU |
| static void | TObject::SetDtorOnly(void* obj) |
| void | SetField(Double_t bx, Double_t by, Double_t bz, Bool_t is_normalized = kTRUE) |
| void | SetHelixStep(Double_t hstep) |
| static void | TObject::SetObjectStat(Bool_t stat) |
| virtual void | TObject::SetUniqueID(UInt_t uid) |
| void | SetXYcurvature(Double_t curvature) |
| virtual void | ShowMembers(TMemberInspector&) |
| void | Step(Double_t step) |
| Double_t | StepToPlane(Double_t* point, Double_t* norm) |
| virtual void | Streamer(TBuffer&) |
| void | StreamerNVirtual(TBuffer& ClassDef_StreamerNVirtual_b) |
| virtual void | TObject::SysError(const char* method, const char* msgfmt) const |
| Bool_t | TObject::TestBit(UInt_t f) const |
| Int_t | TObject::TestBits(UInt_t f) const |
| void | UpdateHelix() |
| virtual void | TObject::UseCurrentStyle() |
| virtual void | TObject::Warning(const char* method, const char* msgfmt) const |
| virtual Int_t | TObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0) |
| virtual Int_t | TObject::Write(const char* name = 0, Int_t option = 0, Int_t bufsize = 0) const |
protected:
| virtual void | TObject::DoError(int level, const char* location, const char* fmt, va_list va) const |
| void | TObject::MakeZombie() |
Data Members
public:
| enum EGeoHelixTypes { | kHelixNeedUpdate | |
| kHelixStraigth | ||
| kHelixCircle | ||
| }; | ||
| enum TObject::EStatusBits { | kCanDelete | |
| kMustCleanup | ||
| kObjInCanvas | ||
| kIsReferenced | ||
| kHasUUID | ||
| kCannotPick | ||
| kNoContextMenu | ||
| kInvalidObject | ||
| }; | ||
| enum TObject::[unnamed] { | kIsOnHeap | |
| kNotDeleted | ||
| kZombie | ||
| kBitMask | ||
| kSingleKey | ||
| kOverwrite | ||
| kWriteDelete | ||
| }; |
private:
| Double_t | fB[3] | normalized direction for magnetic field |
| Double_t | fC | curvature in XY plane |
| Double_t | fDir[3] | direction after a step |
| Double_t | fDirInit[3] | normalized initial direction |
| TGeoHMatrix* | fMatrix | transformation of local helix frame to MARS |
| Double_t | fPhi | phi angle |
| Double_t | fPoint[3] | point after a step |
| Double_t | fPointInit[3] | initial point |
| Int_t | fQ | right/left-handed (+/- 1) - "charge" |
| Double_t | fS | Z step of the helix / 2*PI |
| Double_t | fStep | current step |
Class Charts
Function documentation
Double_t ComputeSafeStep(Double_t epsil = 1E-6) const
Compute safe linear step that can be made such that the error between linear-helix extrapolation is less than EPSIL.
void InitPoint(Double_t x0, Double_t y0, Double_t z0)
Initialize coordinates of a point on the helix
void InitDirection(Double_t dirx, Double_t diry, Double_t dirz, Bool_t is_normalized = kTRUE)
Initialize particle direction (tangent on the helix in initial point)
void InitDirection(Double_t* dir, Bool_t is_normalized = kTRUE)
Initialize particle direction (tangent on the helix in initial point)
void SetField(Double_t bx, Double_t by, Double_t bz, Bool_t is_normalized = kTRUE)
Initialize particle direction (tangent on the helix in initial point)
void Step(Double_t step)
Make a step from current point along the helix and compute new point, direction and angle To reach a plane/ shape boundary, one has to: 1. Compute the safety to the plane/boundary 2. Define / update a helix according local field and particle state (position, direction, charge) 3. Compute the magnetic safety (maximum distance for which the field can be considered constant) 4. Call TGeoHelix::Step() having as argument the minimum between 1. and 3. 5. Repeat from 1. until the step to be made is small enough. 6. Add to the total step the distance along a straigth line from the last point to the plane/shape boundary
Double_t StepToPlane(Double_t* point, Double_t* norm)
Propagate initial point up to a given Z position in MARS.