The MapsTrack Library

An analysis and simple persistency library for tracking with MAPS sensors.

Jamie Ballin, Imperial College London Feburary 2008

Overview

Classes are provided to build candidate tracks from 3 or 4 hits in 3 or 4 sensors. Sensors are placed (by the user) into a global coordinate system. The user specifies track quality cuts, and tracks are interrogated for the likelihood that they are real tracks. The classes provide facilities for:

• global sensor alignment and geometry
• determination of hit "residuals"
• efficiency calculation of sensors (as a function of time, spatial position, pixel architecture, and threshold)
• persistency of the track data to a ROOT file
• ability to quickly reprocess tracks without recreating them from "raw data"

Sensors are told when they are efficient, and when they are not for each track. Once all the tracks have been processed, sensors may be queried for relevant plots.

The MapsTrackManager class provides simple persistency for track and sensors: once you've populated an instance of the class with tracks (see MapsTrack) and sensors (see MapsSensor), it may persist them to a Root file. The data is stored in the format of a Root TTree. A MapsTrackManager can recreate its state from the saved file.

NOTE: the only truly persistent data are the raw pixel coordinates of the track and their assosciated sensor IDs. Everything else can be readjusted.

Various executables are supplied in tests/ for the user's delectation and enjoyment.

Usage

The library is organised into two parts:

• libMapsTrack.so contains the MapsTrack, MapsSensor and MapsTrackManager classes discussed above.
• tests/ contains exectuables which are built and linked to libMapsTrack.so. Users should write their own executables following in this fashion.

Makefiles are supplied in the root directory to build the library, and in the tests/ directory to build executables.

Make sure you export LD_LIBRARY_PATH=[path to maps tracks]/lib:$LD_LIBRARY_PATH otherwise your executables won't work!

One should take advantage of the Root file that the MapsTrackManager class exports: the format of the Root TTree contained therein allows you to explore the data extremely easily, and make dynamic cuts. Having opened the file in a TBrowser, right-click on the tree and select "Open Viewer...". See the Root documentation for further details.

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