Consider the region \( R = \{(x,y) \in \mathbb{R} \times \mathbb{R} : x \geq 0 \text{ and } y^2 \leq 4 - x\} \). Let \( F \) be the family of all circles that are contained in \( R \) and have centers on the \( x \)-axis. Let \( C \) be the circle that has largest radius among the circles in \( F \). Let \( (\alpha, \beta) \) be a point where the circle \( C \) meets the curve \( y^2 = 4 - x \).
The value of \( \alpha \) is ________.
