Renormalization of the Classical Velocity in the Lattice Heavy Quark Effective Theory

In the lattice formulation of the Heavy Quark Effective Theory (LHQET), the classical velocity becomes renormalized. The origin of this renormalization is the reduction of Lorentz (or O(4)) invariance to (hyper)cubic invariance. The renormalization is finite, depends on the form of the discretization of the reduced heavy quark Dirac equation, and can persist down to zero lattice spacing. For the Forward Time - Centered Space discretization, the renormalization is computed both perturbatively, to one loop, and non-perturbatively using an ensemble of lattices provided by the Fermilab ACP-MAPS collaboration. The estimates of the leading multiplicative shift agree reasonably well, and indicate that to first order, the classical velocity is reduced by about 20-25%.