A particle of mass \(m\) moves along the positive \(x\)-axis in a region where its potential energy \(U(x)\) is given by \(U(x) = U_0 \left[ \left(\dfrac{d}{x}\right)^2 - 2\left(\dfrac{d}{x}\right) \right]\), where \(U_0\) and \(d\) are positive constants. The particle is displaced slightly from its stable equilibrium position and released from rest. What is the angular frequency \(\omega\) of small oscillations of the particle about this equilibrium position?