Charge Symmetry Breaking Effects on Neutron Beta Decay in Non-Relativistic Quark Models

A formalism for the study of charge symmetry breaking (CSB) effects is discussed and used to analyze the effects of charge symmetry breaking on neutron beta decay. The effect of including CSB reduces the beta decay matrix element by an amount on the order of ${10}^{-4}$, a value much larger than the previous estimate. A much smaller contribution due to proton recoil is treated as well, which is found to be on the order of ${10}^{-6}$. The current uncertainty in the value of $V_{ud}$ is also of order ${10}^{-4}$. An improvement of that uncertainty by an order of magnitude would require that charge symmetry breaking effects should be included in future analyses.