\documentclass{book}

\usepackage{ptext}
\usepackage{xepersian}
\settextfont[Scale=1]{Yas}  %فونت پیش‌فرض فارسی

% XePersian macro in the xepersian package is defined as below:
%\def\XePersian{\leavevmode$\smash{\hbox{X\lower.5ex\hbox{\kern-.125em\bidi@reflect@box{E}}Persian}}$}

\begin{document}
\chapter{نماد \XePersian}
\ptext
\chapter{نماد \protect\XePersian}
\ptext
\end{document}