  Persistence of spatial analyticity is studied for solution of the beam
equation $ u_{tt} + \left(m+\Delta^2\right) u + |u|^{p-1}u = 0$ on $\mathbb R^n
\times \mathbb R$. In particular, for a class of analytic initial data with a
uniform radius of analyticity $\sigma_0$, we obtain an asymptotic lower bound
$\sigma(t) \ge c/\sqrt t$ on the uniform radius of analyticity $\sigma(t)$ of
solution $u(\cdot, t)$, as $t \rightarrow \infty.$
