test.tex

\documentclass[unicode]{beamer}
\usepackage[no-math,ipaex]{luatexja-preset}
\renewcommand{\kanjifamilydefault}{\gtdefault}

\usefonttheme{professionalfonts}

\usepackage{unicode-math}
\setmathfont{xits-math.otf}

\begin{document}

\begin{frame}{テスト}
\[
        f(x) = \frac{1}{\sqrt{2\pi\sigma^2}}\exp\left(-\frac{(x-\mu)^2}{2\sigma^2}\right)
\]
\end{frame}

\end{document}