Arc Circle Syntax

I cannot find any information on what the tex command is to create the arc symbol over letters like the following image: http://www.mathwarehouse.com/images/questions/arc/arc-CH_CCCCFF.jpg

Does anyone know the tex for this (which I hope MathJax supports ;)

---

If you add

    <script type="text/x-mathjax-config">
      MathJax.Hub.Config({
        TeX: { Augment: {
          Definitions: {
            macros: {
              overparen: ['UnderOver','23DC'],
              underparen: ['UnderOver','23DD']
            }
          }
        }}
      });
    </script>

before the script that loads MathJax.js, then you can use

    $\overparen{\rm CH}$

to get a paren over the CH. This is not exactly what you have, but it is close.