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Manuscript Title: A track matching program for bubble chamber photographs.
Authors: P.L. Bastien, J.N. Snyder, V. Pless
Program title: MATCH
Catalogue identifier: ABCB_v1_0
Distribution format: gz
Journal reference: Comput. Phys. Commun. 2(1971)394
Programming language: Fortran.
Computer: IBM 360-65.
Operating system: 0S 360.
Program overlaid: yes
RAM: 30K words
Word size: 32
Keywords: Nuclear physics, High energy, Bubble chamber, Track matching, First order optics, Particle detection.
Classification: 17.5.

Nature of problem:
Bubble chamber events are photographed by three cameras. Given sets of unlabeled track measurements in each of the three views, the program labels corresponding tracks.

Solution method:
There are two distinct steps in the solution: (i) We use the simplest possible geometric situation (all indices of refraction set to 1) to find potential triples of tracks. (a) We eliminate all pairs of tracks which could not possibly have come from the same track in space. A pair is defined as a track measurement in view i together with a track measurement in view j(i is not =j). (b) We construct for all triples of tracks surviving the pair test an estimator which in principle should be zero if the three tracks belong to the same track in space. Because of our crude geometrical approximation the estimator cut-off must be set high and some related triples will in general remain after the test. (ii) We now rely on logic to separate related triples. A set of related triples can be shown to form an equivalence class. The equivalence classes are processed through a routine which finds the maximal independent set of triples for the class.

The program is quite general since it can handle an unequal number of tracks in each view. For example the input could consist of the track measurements for an interaction plus random extraneous tracks in each view. Furthermore, since tracks measured with automatic devices usually have large gaps or sometimes sections missing entirely, the minimum percentage overlap between the tracks of a pair is an adjustable parameter.