LaTeX.org

Thank you very much ^_^

Hello world ^_^
I'm new in this community and I have a question for you:
I want to write this:
integrale1.png
but if i write on my LaTeX editor:
\int_{ \hat{\sigma}_{\mathrm{peak}} \sqrt{\mathrm{PCE_{peak}}} }^{\infty}
\frac{1}{\sqrt{2\pi\hat{\sigma}_i^2}} e^{\frac{x^2}{2\hat{\sigma}_i^2 ...