hep.lcd.util.swim
Class HelixSwim

java.lang.Object
  |
  +--hep.lcd.util.swim.HelixSwim

public class HelixSwim

extends Object

Given a particle of initial momentum, position and charge (p, r0 and iq), calculates its trajectory in a uniform magnetic field in the z-direction. The trajectory is parametrized as function of the path length alpha.
This implementation works for charged and neutral particles alike. Note: This class has been specifically adapted to the unique LCD tracking coordinate system. (Inverted sign of curvatures.)

Version:

$Id: HelixSwim.java,v 1.2 2001/06/18 22:39:12 walkowia Exp $

Author:

W.Walkowiak

Source Code:

HelixSwim.java

Field Summary

static double

PTINY public static constants

Constructor Summary

HelixSwim(double B)
Create a helix swimmmer.

HelixSwim(double B, double[] p, double[] r0, int iq)
Create and initialize a helix swimmmer.

HelixSwim(double B, double rhoMin, double rhoMax, double zMax)
Create a helix swimmmer set B field and cylindrical geometry parallel to z-axis.

Method Summary

Vector	asPoints(double alphaMax) Provide points along the particle's track within cylindrical volume.
double	getCosL() report cos lambda
double	getRc() report the circle's radius in the rho-phi plane
double	getSinL() report sin lambda
double	getTanL() report tan lambda
void	setCurvatureFlip(boolean isFlipped) Flag for flipped curvature.
void	setCylinderGeometry(double rhoMin, double rhoMax, double zMax) Set cylindrical geometry parallel to z-axis.
void	setPointDensity(int nPoints) Set minimum point number on a full circle.
void	setPointDistance(double ptDist) Set point distance along trajectory:
void	setTrack(double[] p, double[] r0, int iq) Set track for helix swimmmer.
double[]	swimBy(double alpha) swim along this track to point at distance alpha from it's origin (in positive track direction)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

PTINY

public static final double PTINY

public static constants

Constructor Detail

HelixSwim

public HelixSwim(double B)

Create a helix swimmmer.

Parameters:

B - field strength; uniform, solenoidal, directed along z-axis

HelixSwim

public HelixSwim(double B,
                 double rhoMin,
                 double rhoMax,
                 double zMax)

Create a helix swimmmer set B field and cylindrical geometry parallel to z-axis.

Parameters:

B - field strength; uniform, solenoidal, directed along z-axis

rhoMin - minimum radius

rhoMax - maximum radius

zMax - maximum extend in +/-z

See Also:

setCylinderGeometry(double, double, double)

HelixSwim

public HelixSwim(double B,
                 double[] p,
                 double[] r0,
                 int iq)

Create and initialize a helix swimmmer.

Parameters:

B - field strength; uniform, solenoidal, directed along z-axis

p - 3-momentum (px,py,pz)

r0 - initial position(x0,y0,z0)

iq - charge iq = q/|e| = +/-1

Method Detail

setTrack

public void setTrack(double[] p,
                     double[] r0,
                     int iq)

Set track for helix swimmmer. Note: This method is LCD specific because of the wrong curving direction of all tracks in the LCD software environment.

Parameters:

B - field strength; uniform, solenoidal, directed along z-axis

p - 3-momentum (px,py,pz)

r0 - initial position(x0,y0,z0)

iq - charge iq = q/|e| = +/-1

swimBy

public double[] swimBy(double alpha)

swim along this track to point at distance alpha from it's origin (in positive track direction)

getRc

public double getRc()

report the circle's radius in the rho-phi plane

getTanL

public double getTanL()

report tan lambda

Returns:

tangent of the dip angle lambda

getSinL

public double getSinL()

report sin lambda

Returns:

sine of the dip angle lambda

getCosL

public double getCosL()

report cos lambda

Returns:

cosine of the dip angle lambda

setPointDensity

public void setPointDensity(int nPoints)

Set minimum point number on a full circle.

Parameters:

nPoints - number of points on a full circle

See Also:

asPoints(double)

setPointDistance

public void setPointDistance(double ptDist)

Set point distance along trajectory:

Parameters:

ptDist - distance between two points

See Also:

asPoints(double)

setCylinderGeometry

public void setCylinderGeometry(double rhoMin,
                                double rhoMax,
                                double zMax)

Set cylindrical geometry parallel to z-axis.

Parameters:

rhoMin - minimum radius

rhoMax - maximum radius

zMax - maximum extend in +/-z

See Also:

asPoints(double)

asPoints

public Vector asPoints(double alphaMax)

Provide points along the particle's track within cylindrical volume.

Parameters:

alphaMax - : maximum path length along trajectory, alphaMax < 0 : alphaMax is automatically set according to the cylinders extensions.

Returns:

Vector of double[3] containing points on trajectory.

See Also:

setCylinderGeometry(double, double, double), setPointDistance(double), setPointDensity(int)

setCurvatureFlip

public void setCurvatureFlip(boolean isFlipped)

Flag for flipped curvature.
This enables us to compare this Helix with GISMO hits for example.