Properties of the hypercharge sector of the standard model on the lattice

Using a hopping parameter expansion, we demonstrate the decoupling of fermion doubler modes in the hypercharge U(1)_Y lattice gauge theory. We also show analytically that it is possible to tune the bare Yukawa coupling to a value such that the fundamental physical fermion am_f=0 (as is necessary in order to obtain a finite physical mass m_f in the continuum limit), and we calculate this value. The appropriate special case of these results is compared with numerical simulations of the frozen-gauge limit of the U(1)_Y theory, and good agreement is found. The role of the Yukawa coupling in a chiral lattice gauge theory is contrasted with that in a nonchiral Yukawa model.