org.lcsim.fit.helicaltrack

Class HelicalTrackCross

java.lang.Object

org.lcsim.fit.helicaltrack.HelicalTrackHit

org.lcsim.fit.helicaltrack.HelicalTrackCross

All Implemented Interfaces:

Comparable, TrackerHit

public class HelicalTrackCross
extends HelicalTrackHit

Encapsulate cross (stereo) hit information needed by HelicalTrackFitter. The separation between the two sensor planes makes the hit position and covariance matrix depend on the track direction (track curvature between the sensor planes is assumed to be negligible). The nominal hit position is calculated assuming the track originates from the origin. A corrected hit position and covariance matrix, which accounts for the track direction and uncertainties in the track direction, can be calculated as well. Note that the nominal position will have large uncertainties associated with not knowing the track direction.

Version:

1.0

Author:

Richard Partridge

Field Summary

Fields

Modifier and Type	Field and Description
private HelicalTrackFit	_helix
private HelicalTrackStrip	_strip1
private HelicalTrackStrip	_strip2
private static int	_type

Fields inherited from class org.lcsim.fit.helicaltrack.HelicalTrackHit

_eps, _epsParallel, _epsStereoAngle, id

Constructor Summary

Constructors

Constructor and Description
HelicalTrackCross() Creates a new instance of HelicalTrackCross
HelicalTrackCross(HelicalTrackStrip strip1, HelicalTrackStrip strip2) Creates a new instance of HelicalTrackCross

Method Summary

Methods

Modifier and Type	Method and Description
private double	ChisqPenalty(TrackDirection trkdir, SymmetricMatrix hcov) Calculate a chi^2 penalty if one or both unmeasured coordinates for the hit lie outside the extant of their respective strips.
List<HelicalTrackStrip>	getStrips() Return a list of HelicalTrackStrips that contains the two strips that form the cross.
private void	init()
void	init(HelicalTrackStrip strip1, HelicalTrackStrip strip2)
void	resetTrackDirection() Reset the corrected hit position and covariance matrix to their nominal values (i.e., for a track coming from the origin with unknown track direction).
void	setTrackDirection(HelicalTrackFit helix)
void	setTrackDirection(TrackDirection trkdir, SymmetricMatrix hcov) Set the track direction to be used in calculating the corrected position and covariance matrix.

Methods inherited from class org.lcsim.fit.helicaltrack.HelicalTrackHit

addMCParticle, addRawHit, BarrelEndcapFlag, chisq, compareTo, Detector, dr, drcalc, drphi, drphicalc, getCellID, getCorrectedCovMatrix, getCorrectedPosition, getCovMatrix, getdEdx, getEdepError, getEpsParallel, getLayerIdentifier, getMCParticles, getPosition, getQuality, getRawHits, getTime, getType, init, Layer, phi, r, setChisq, setCorrectedCovMatrix, setCorrectedPosition, setEpsParallel, setEpsStereoAngle, setPosition, toString, x, y, z

Methods inherited from class java.lang.Object

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

Field Detail

_strip1

private HelicalTrackStrip _strip1

_strip2

private HelicalTrackStrip _strip2

_helix

private HelicalTrackFit _helix

_type

private static int _type

Constructor Detail

HelicalTrackCross

public HelicalTrackCross(HelicalTrackStrip strip1,
                 HelicalTrackStrip strip2)

Creates a new instance of HelicalTrackCross

Parameters:

strip1 - First of the two strips that form this cross

strip2 - Second of the two strips that form this cross

HelicalTrackCross

public HelicalTrackCross()

Creates a new instance of HelicalTrackCross

Method Detail

init

public void init(HelicalTrackStrip strip1,
        HelicalTrackStrip strip2)

init

private void init()

getStrips

public List<HelicalTrackStrip> getStrips()

Return a list of HelicalTrackStrips that contains the two strips that form the cross.

Returns:

list of the two strips that form this cross

setTrackDirection

public void setTrackDirection(HelicalTrackFit helix)

setTrackDirection

public void setTrackDirection(TrackDirection trkdir,
                     SymmetricMatrix hcov)

Set the track direction to be used in calculating the corrected position and covariance matrix. Calling this method will cause the corrected position and covariance matrix to be recalculated and stored and stored in the parent class.

Parameters:

trkdir - TrackDirection object containing direction and derivatives

hcov - covariance matrix for helix parameters

resetTrackDirection

public void resetTrackDirection()

Reset the corrected hit position and covariance matrix to their nominal values (i.e., for a track coming from the origin with unknown track direction). This method should be called before the first attempt to fit a helix to erase the "memory" of the previous helix fit. Once there is some knowledge of the track direction (eg from one or more previous helix fits), invoking the setTrackDirection method will update the hit position and covariance matrix and significantly improve the hit position resolution for cross hits.

ChisqPenalty

private double ChisqPenalty(TrackDirection trkdir,
                  SymmetricMatrix hcov)

Calculate a chi^2 penalty if one or both unmeasured coordinates for the hit lie outside the extant of their respective strips.

Parameters:

trkdir - track direction

hcov - helix covariance matrix

Returns:

chi^2 penalty