Extra symmetries in the effective theory of heavy quarks

Abstract

Extra symmetries are shown to exist in the effective theory of heavy quarks when both quarks and anti-quarks with the same velocity are included. These symmetries mix the quark with the anti-quark sector and they resemble axial-type of symmetries. Together with the known flavor and spin symmetries they form a $u(4)$ algebra when a single flavor is considered. It is shown that the full $U(4)$ set of symmetries breaks spontaneously down to $ U(2) \otimes U(2)$. The Goldstone modes corresponding to the spontaneously broken currents are identified. Finally, the precise connection of this theory with the fundamental QCD is derived and it is investigated under some approximations. Some physical processes where these extra symmetries may be relevant are pointed out.