Class SwimZ

java.lang.Object

cnuphys.swimZ.SwimZ

public class SwimZ
extends Object

This class holds the parameters and static methods for the swimZ integration. The swimZ integration follows the method described for the HERA-B magnet here: http://arxiv.org/pdf/physics/0511177v1.pdf

The state vector has five elements:
(x, y, tx, ty, q)
Where x and y are the transverse coordinates (meters), tx = px/pz, ty = py/pz, and q = Q/|p| where Q is the integer charge (e.g. -1 for an electron)

UNITS

• x, y, and z are in cm
• p is in GeV/c
• B (mag field) is in kGauss

Author:

heddle

Field Summary

Fields

Modifier and Type	Field	Description
static final double	ARGONRADLEN	Argon radiation length in cm
static final double	C	The speed of light in these units: (GeV/c)(1/kG)(1/cm)

Constructor Summary

Constructors

Constructor	Description
SwimZ()	SwimZ constructor.
SwimZ(IMagField magneticField)	Create a swimmer specific to a magnetic field
SwimZ(MagneticField magneticField)	Create a swimmer specific to a magnetic field

Method Summary

Modifier and Type	Method	Description
SwimZResult	adaptiveRK(int Q, double p, SwimZStateVector start, double zf, double stepSize, double[] hdata)	Swim to a fixed z over short distances using RK adaptive stepsize
int	adaptiveRK(int Q, double p, SwimZStateVector start, SwimZStateVector stop, double zf, double stepSize, double[] hdata)	Swim to a fixed z using RK adaptive stepsize
double	getEps()	Get the tolerance used by the CLAS_Toleance array
FieldProbe	getProbe()	Get the underlying field probe
SwimZResult	parabolicEstimate(int Q, double p, SwimZStateVector start, double zf, double stepSize)	Swim to a fixed z over short distances using a parabolic estimate
void	parabolicEstimate(int Q, double p, SwimZStateVector start, SwimZStateVector stop, double zf)	Swim to a fixed z over short distances using a parabolic estimate, without intermediate points
SwimZResult	sectorAdaptiveRK(int sector, int Q, double p, SwimZStateVector start, double zf, double stepSize, double[] hdata)	Swim to a fixed z over short distances using RK adaptive stepsize
void	setAbsoluteTolerance(double eps)	Set the tolerance used by the CLAS_Tolerance array

Methods inherited from class java.lang.Object

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

Field Details

C

public static final double C

The speed of light in these units: (GeV/c)(1/kG)(1/cm)

See Also:

• Constant Field Values

ARGONRADLEN

public static final double ARGONRADLEN

Argon radiation length in cm

See Also:

• Constant Field Values

Constructor Details

SwimZ

public SwimZ()

SwimZ constructor. Here we create a Swimmer that will use the given magnetic field.

Parameters:

field - interface into a magnetic field

SwimZ

public SwimZ(MagneticField magneticField)

Create a swimmer specific to a magnetic field

Parameters:

magneticField - the magnetic field

SwimZ

public SwimZ(IMagField magneticField)

Create a swimmer specific to a magnetic field

Parameters:

magneticField - the magnetic field

Method Details

getProbe

public FieldProbe getProbe()

Get the underlying field probe

Returns:

the probe

setAbsoluteTolerance

public void setAbsoluteTolerance(double eps)

Set the tolerance used by the CLAS_Tolerance array

Parameters:

eps - the baseline absolute tolerance.

getEps

public double getEps()

Get the tolerance used by the CLAS_Toleance array

Returns:

the tolerance used by the CLAS_Toleance array

adaptiveRK

public SwimZResult adaptiveRK(int Q,
 double p,
 SwimZStateVector start,
 double zf,
 double stepSize,
 double[] hdata)
                       throws SwimZException

Swim to a fixed z over short distances using RK adaptive stepsize

Parameters:

Q - the integer charge of the particle (-1 for electron)

p - the momentum in GeV/c

start - the starting state vector

zf - the final z value (cm)

stepSize - the initial step size

hdata - An array with three elements. Upon return it will have the min, average, and max step size (in that order).

relTolerance - the absolute tolerances on each state variable [x, y, tx, ty] (q = const). So it is an array with four entries, like [1.0e-4 cm, 1.0e-4 cm, 1.0e-5, 1.0e05]

Returns:

the swim result

Throws:

SwimZException

sectorAdaptiveRK

public SwimZResult sectorAdaptiveRK(int sector,
 int Q,
 double p,
 SwimZStateVector start,
 double zf,
 double stepSize,
 double[] hdata)
                             throws SwimZException

Swim to a fixed z over short distances using RK adaptive stepsize

Parameters:

sector - the sector [1..6]

Q - the integer charge of the particle (-1 for electron)

p - the momentum in GeV/c

start - the starting state vector

zf - the final z value (cm)

stepSize - the initial step size

hdata - An array with three elements. Upon return it will have the min, average, and max step size (in that order).

relTolerance - the absolute tolerances on each state variable [x, y, tx, ty] (q = const). So it is an array with four entries, like [1.0e-4 cm, 1.0e-4 cm, 1.0e-5, 1.0e05]

Returns:

the swim result

Throws:

SwimZException

adaptiveRK

public int adaptiveRK(int Q,
 double p,
 SwimZStateVector start,
 SwimZStateVector stop,
 double zf,
 double stepSize,
 double[] hdata)
               throws SwimZException

Swim to a fixed z using RK adaptive stepsize

Parameters:

Q - the integer charge of the particle (-1 for electron)

p - the momentum in Gev/c

start - the starting state vector

stop - will hold the final state vector

zf - the final z value

stepSize - the initial step size

hdata - An array with three elements. Upon return it will have the min, average, and max step size (in that order).

Returns:

the number of steps

Throws:

SwimZException

parabolicEstimate

public void parabolicEstimate(int Q,
 double p,
 SwimZStateVector start,
 SwimZStateVector stop,
 double zf)
                       throws SwimZException

Swim to a fixed z over short distances using a parabolic estimate, without intermediate points

Parameters:

Q - the integer charge of the particle (-1 for electron)

p - the momentum in GeV/c

start - the starting state vector

stop - at end, holds final state vector

zf - the final z value (cm)

Throws:

SwimZException

parabolicEstimate

public SwimZResult parabolicEstimate(int Q,
 double p,
 SwimZStateVector start,
 double zf,
 double stepSize)
                              throws SwimZException

Swim to a fixed z over short distances using a parabolic estimate

Parameters:

Q - the integer charge of the particle (-1 for electron)

p - the momentum in GeV/c

start - the starting state vector

zf - the final z value (cm)

stepSize - the step size

Returns:

the swim result

Throws:

SwimZException