ag.algebraic geometry - Normal bundle of $CP^n$ in $CP^{n+1}$

Let $S^1$ act on $S^{2n+1}$ via Hopf action and $S^1$ also acts on $mathbb{R}^2$ via rotation about the origin.
Then $S^1$ acts on $S^{2n+1}times mathbb{R}^2$ diagonally.

Let $M$ be the quotient of this diagonal action.

My question is why $ M$ can be viewed as the normal bundle of $mathbb {CP}^n$ in $mathbb {CP}^{n+1}$.

I have a feeling that it must be related to the fact that: after removing a $(2n+2)$ disk in $mathbb {CP}^{n+1}$, the boundary $S^{2n+1}$ is fibered over the $mathbb {CP}^n$.

But where can I find the proof of the statement.