UNITY IN PARTICLE PHYSICS: WHY CHOOSE THE PATH OF FOUR COLORS AND LEFT-RIGHT SYMMETRY?

Major progress in unraveling the secrets of nature has been made by finding connections between seemingly unrelated objects and phenomena. This is what one means by the word “Unification”. Some aspects of the quest for unification of the fundamental particles and of their three forces – weak, electromagnetic and strong - will be presented. Starting with the idea of electroweak unification based on the symmetry SU(2)_L x U(1), as it existed in the summer of 1972, it will be explained why a simple aesthetic demand almost uniquely selects out the path to higher unification based on the symmetry of four colors and left-right symmetry. The resulting minimal symmetry is then given by G(2,2,4) = SU(2_L x SU(2) _R x SU(4)-color. The far-reaching consequences and the empirical advantages of this minimal core symmetry, with or without its extension to the simple group SO(10) are noted. These include an understanding of: (i) the observed tiny mass-scales of neutrino oscillations, (ii) aspects of the masses and mixings of all fermions, and (iii) likewise the observed matter-antimatter asymmetry. Predictions of such a unification for the fundamental process of proton decay will be noted.