An alpha particle of mass \(m\) and charge \(+2e\) is projected directly toward a stationary gold nucleus of charge \(+Ze\). When the alpha particle is at a distance \(d\) from the nucleus, it has speed \(v_0\) directed radially inward toward the nucleus. Assuming the gold nucleus remains fixed in place and gravitational forces are negligible, which of the following expressions represents the distance of closest approach \(r_{\text{min}}\) between the alpha particle and the nucleus?