The ALEPH Physics Analysis package ALPHA is intended to simplify Fortran programs for physics analysis. Although all ALEPH data types can be processed with ALPHA, the program is designed primarily for analysis of JULIA output files (POTs), and of DSTs and MINIs. All event input/output is done by ALPHA - the user has to provide only the name(s) of the input/output data set(s). ALPHA also provides easy access to physical variables (e.g., momentum, energy), so the user can write physics analysis programs without detailed knowledge of the ALEPH data structure (tabular BOS banks). An extensive set of utility routines (e.g., kinematics, event shape, secondary vertex finding, b-tagging, MINI-writing, etc.) is available as part of the ALPHA package.
The program structure (Appendix A) is extremely simple. Three Fortran routines are normally supplied by the user: job initialization, event processing, and job termination (see Ch. 3). Reconstructed objects (tracks, vertices, cal. objects) can be accessed with simple DO loops. For Monte Carlo generated events, the MC ``truth'' information is accessible in the same way as reconstructed tracks and vertices (see Ch. 7).
This document describes all features of the ALPHA program. For first-time users, the important parts to read are Ch. 2 (getting started), Ch. 3 (user routines), Ch. 4 (event input), Ch. 7 (loops over tracks), and Ch. 8 (track attributes).
ALPHA has grown up with time , several general utility packages coming from UPHY being incorporated as they become more popular and tested :