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AliRoot » PWGCF » FEMTOSCOPY » ALIFEMTO » AliFmHelix

class AliFmHelix


AliFmHelix: a helper helix class
Includes all the operations and specifications of the helix. Can be
used to determine path lengths, distance of closest approach etc.

Function Members (Methods)

public:

	AliFmHelix(const AliFmHelix&)
	AliFmHelix(double c, double dip, double phase, const AliFmThreeVector<double>& o, int h = -1)
virtual	~AliFmHelix()
AliFmThreeVector<double>	At(double s) const
int	Bad(double WorldSize = 1.e+5) const
double	Curvature() const
double	DipAngle() const
double	Distance(const AliFmThreeVector<double>& p, bool scanPeriods = true) const
int	H() const
virtual void	MoveOrigin(double s)
AliFmHelix&	operator=(const AliFmHelix&)
const AliFmThreeVector<double>&	Origin() const
pair<double,double>	PathLength(double r) const
double	PathLength(const AliFmThreeVector<double>& p, bool scanPeriods = true) const
double	PathLength(const AliFmThreeVector<double>& r, const AliFmThreeVector<double>& n) const
double	PathLength(double x, double y) const
pair<double,double>	PathLength(double r, double x, double y, bool scanPeriods = true)
pair<double,double>	PathLengths(const AliFmHelix& h, bool scanPeriods = true) const
double	Period() const
double	Phase() const
void	SetParameters(double c, double dip, double phase, const AliFmThreeVector<double>& o, int h)
bool	Valid(double world = 1.e+5) const
double	X(double s) const
double	XCenter() const
double	Y(double s) const
double	YCenter() const
double	Z(double s) const

protected:

	AliFmHelix()
double	FudgePathLength(const AliFmThreeVector<double>& v) const
void	SetCurvature(double d)
void	SetDipAngle(double d)
void	SetPhase(double d)

Data Members

public:

static const double	fgkNoSolution	coinstant indicating lack of solution

protected:

double	fCosDipAngle	cosine of the dip angle
double	fCosPhase	cosine of the phase
double	fCurvature	curvature
double	fDipAngle	Helix dip angle
int	fH	-sign(q*B);
AliFmThreeVector<double>	fOrigin	Helix origin
double	fPhase	phase
double	fSinDipAngle	sine of the dip angle
double	fSinPhase	sine of the phase
bool	fSingularity	true for straight line case (B=0)

Class Charts

Inheritance Chart:

AliFmHelix

←

AliFmPhysicalHelix

Function documentation

AliFmHelix()

Default constructor
noop

AliFmHelix(double c, double dip, double phase, const AliFmThreeVector<double>& o, int h = -1)

 Constructor with helix parameters

~AliFmHelix()

 Default destructor
noop

void SetParameters(double c, double dip, double phase, const AliFmThreeVector<double>& o, int h)

  The order in which the parameters are set is important
  since setCurvature might have to adjust the others.

void SetCurvature(double d)

 Set helix curvature

void SetPhase(double d)

 Set helix phase

void SetDipAngle(double d)

 Set helix dip angle

double XCenter() const

 Set helix center in X

double YCenter() const

 Set helix center in Y

double FudgePathLength(const AliFmThreeVector<double>& v) const

 Path length

double Distance(const AliFmThreeVector<double>& p, bool scanPeriods = true) const

 calculate distance between origin an p along the helix

double PathLength(const AliFmThreeVector<double>& p, bool scanPeriods = true) const

  Returns the path length at the distance of closest
  approach between the helix and point p.
  For the case of B=0 (straight line) the path length
  can be calculated analytically. For B>0 there is
  unfortunately no easy solution to the problem.
  Here we use the Newton method to find the root of the
  referring equation. The 'fudgePathLength' serves
  as a starting value.

double Period() const

 period

pair<double, double> PathLength(double r) const

 The math is taken from Maple with C(expr,optimized) and
 some hand-editing. It is not very nice but efficient.
 'first' is the smallest of the two solutions (may be negative)
 'second' is the other.

pair<double, double> PathLength(double r, double x, double y, bool scanPeriods = true)

 path length

double PathLength(const AliFmThreeVector<double>& r, const AliFmThreeVector<double>& n) const

 Vector 'r' defines the position of the center and
 vector 'n' the normal vector of the plane.
 For a straight line there is a simple analytical
 solution. For curvatures > 0 the root is determined
 by Newton method. In case no valid s can be found
 the max. largest value for s is returned.

PathLengths(const AliFmHelix& h, bool scanPeriods = true) const

	Cannot handle case where one is a helix
  and the other one is a straight line.

void MoveOrigin(double s)

 Move the helix origin

int H() const

     Inline functions

{return fH;}

double DipAngle() const

{return fDipAngle;}

double Curvature() const

{return fCurvature;}

double Phase() const

{return fPhase;}

double X(double s) const

double Y(double s) const

double Z(double s) const

const AliFmThreeVector<double>& Origin() const

{return fOrigin;}

AliFmThreeVector<double> At(double s) const

double PathLength(double x, double y) const

int Bad(double WorldSize = 1.e+5) const

AliFmHelix(double c, double dip, double phase, const AliFmThreeVector<double>& o, int h = -1)

 curvature, dip angle, phase, origin, h

bool Valid(double world = 1.e+5) const

 checks for valid parametrization

{return !Bad(world);}