The High Energy Physics (HEP) [1] – often called Particle Physics – is one of the research areas where the accomplishment of scientific results is inconceivable without the infrastructure for distributed computing, the Computing Grid. The HEP is a branch of Physics that studies properties of elementary subatomic constituents of matter. It goes beyond protons and neutrons to study particles which existed only a fraction of a second after the Big Bang and quarks and gluons in the so-called Quark Gluon Plasma (QGP) [2]. These studies are based on experiments with particles colliding at very high energies, at speeds almost equal to the speed of light.