I want to plot the following illustration in mathematica.

1. First I need to plot a half open interval $(a,b]$ on a real line (ticks and labels are not needed).
2. Then I need a piece of symmetric curve over "$b$" to indicate the neighborhood of $b$ with radius $\epsilon$.

I am not familiar with such plot. Can anyone provide some help. Thank you!

[![enter image description here](https://i.stack.imgur.com/qXVF2.png)](https://i.stack.imgur.com/qXVF2.png)