DF Definitions of Tracking Elements

Below are definitions of the structures used in the clas12 dc reconstructions.

Hits

Hit.java

The basic building block of the other structures used in the reconstruction, Hits are simply a representation of a drift chamber wire interaction. It stores all of the relevant information for identifying a wire:

Sector	Which of the six radial sectors the hit is in.
Superlayer	Which of the six superlayers the hit is in.
Layer	Which of the six wire plane layers within the superlayer the hit is in.
Wire	The wire within the layer the hit is in.
TDC	The Time-to-Digital Converter which processed the hit

And some information about the interaction itself:

ID	The hit index in the Evio column.
Cell Size	The size of the wire cell. The wires are arranged in hexagonal cells, but different layers have different sizes of hexagons.
DoCA Error	Uncertainty in the distance of closest approach time.

It should be noted that this implements the Comparable interface; that is to say the the function compareTo() has been implemented such that hits can be absolutely ordered. The ordering appears to be exactly as you would expect: Sector > SuperLayer > Layer > Wire. This allows you to call the built in sort function of ArrayLists of Hits (such as Clusters).

FittedHit.java

An extension of Hit.java which is meant to be used in fitted clusters, this includes additional information:

X

XMP

Z

lX

lY

Residual

Time Residual

Left-Right Ambiguity

Quality Fac

Tracking Status

Cluster Fit DOCA