A small mass particle is given an initial velocity \(\mathbf{v}_{0}\) tangent to the horizontal rim of a smooth hemispherical bowl at a radius \(r_{0}\) from the vertical centerline, as shown at point \(A\). As the particle slides past point \(B\), a distance \(h\) below \(A\) and a distance \(r\) from the vertical centerline, its velocity \(\mathbf{v}\) makes an angle \(\theta\) with the horizontal tangent to the bowl through \(B\). Determine \(\theta\).

h r B