Aim of this step is to discriminate the signal produced by the ionization electrons from the electronic noise.
Procedure searches independently every wire for hits, which are considered to be an output signal regions of a certain width and amplitude above the local mean value (baseline).
Fine hit reconstruction
To obtain the physical information from the identified hits, signal from every hit is fitted with an analytical function in a certain area. This operation derrives the parameters such as position, height and area of the hit.
Cluster is a group of the adjacent hits in the wire-drift coordinates plane.
In this step the hits belonging to the common charge deposition distrubutions, such as tracks and showers, are grouped. The goal of this procedure is to provide the identification criteria for the different patterns as well as help to discriminate between signal and noise hits.
3D hit reconstruction
Hit spatial coordinates are reconstructed using the combined information from different views (wire planes). Each wire plane gives constrains on the two spatial degrees of freedom of the hit. One constrain is common - it's the drift time and one is wire coordinate, which is specific for each wire plane. Associating the hits from at least two planes allows to determinate the spatial coordinates of the hits.