## Suppressing flavor-changing neutral current interactions from leptoquark exchange by a family symmetry

It is shown that the flavor-changing neutral current interaction of leptoquark exchange can be strongly suppressed by a global family symmetry without a numerical fine-tuning of the parameters. In the symmetry limit, if n{times}n degenerate leptoquarks couple universally to n generations of quarks and leptons in the weak basis, not only is the neutral current interaction flavor diagonal, but also the charged current interaction takes exactly the same form as W exchange at low energies. Neutrino reactions and atomic parity violation still impose tight constraints. A quantitative analysis is made on the stability of flavor diagonalization and family independence againstmore »