A small particle of mass \(m\) and charge \(+q\) is launched from a large distance with initial speed \(v_0\) toward a fixed point charge \(+Q\). The initial line of motion is offset from \(+Q\) by an impact parameter \(b\). Let \(d_0 = \dfrac{q Q}{2\pi\varepsilon_0 m v_0^2}\) be the distance of closest approach for a head-on collision (\(b = 0\)). Which of the following expressions gives the distance of closest approach \(r_{\text{min}}\) for a trajectory with a non-zero impact parameter \(b\)?