8. Let $F_{1}, F_{2}$ be the left and right foci of the hyperbola $\frac{x^{2}}{a^{2}}-\frac{y^{2}}{b^{2}}=1(a>0, b>0)$, respectively. If there exists a point $P$ on the right branch of the hyperbola such that $\left(\overrightarrow{O P}+\overrightarrow{O F_{2}}\right) \cdot \overrightarrow{P F_{2}}=0$, where $O$ is the origin, and $\left|\overrightarrow{P F_{1}}\right|=\sqrt{3}\left|\overrightarrow{P F_{2}}\right|$, then the eccentricity of the hyperbola is $\qquad$.