Experiment Proposal - opera - Infn

6 Readout and data analysis of the ECC bricks
6.1 Introduction
As shown schematically in Fig. 99, the selected brick is extracted from the detector and disassembled
after exposure to cosmic rays for alignment purposes. The emulsion films are developed and transported
to the readout facilities in order to perform the second level data taking, namely the extraction of the
event information from the emulsion.
ν τ
Figure 99: Brick handling procedures.
The Track Selector [9] automate the readout of track information from the emulsion films. Before
describing the different steps of the data analysis, we define some terms frequently used in the following.
The track segments recognised by the Track Selector in an emulsion layer of a film are called
microtracks. The Track Selector tries to associate the micro tracks found in both layers of a film
and, if successful, the two connected micro tracks form a basetrack. Base tracks from different films are
aligned and connected by software. A set of connected base tracks defines a track.
The Track Selector works in two different modes, the Point Scan and the General Scan mode, defined
as follows
Point Scan: searches for a base track with a predicted angle and position. The Track Selector reads
out images in an area whose extension is determined by the accuracy of the predicted position, and
tries to recognise a micro track in an angular range limited by the prediction angular accuracy and
by the possible distortion of the emulsion layers. The existence of a corresponding micro track on
the other side of the film is then looked for.
General Scan: reads out all base tracks with any position and angle in a given scanning area of one
film.Thisinformationisstoredonanintermediatediskstorage.
128