Recent enhancements to the MARS15 code

The MARS code is under continuous development and has recently undergone substantial improvements that further increase its reliability and predictive power in numerous shielding, accelerator, detector and space applications. The major developments and new features of the MARS15 (2004) version described in this paper concern an extended list of elementary particles and arbitrary heavy ions and their interaction cross-sections, inclusive and exclusive nuclear event generators, module for modeling particle electromagnetic interactions, enhanced geometry and histograming options, improved MAD-MARS Beam Line Builder, enhanced Graphical-User Interface, and an MPI-based parallelization of the code