\hat allowed only in math mode

\newcommand{\bx}{\mathbf{x}}
\newcommand{\by}{\mathbf{y}}

\begin{eqnarray*}
{\hat{\bx}}_1&=&\by_5[1:L],& {\hat{\bx}}_3&=&\by_3[1:L],\
{\hat{\bx}}_2&=&\by_4[2:L+1],\quad & {\hat{\bx}}_4&=&\by_2[2:L+1],\
& & & {\hat{\bx}}_5&=&\by_1[1:L],
\end{eqnarray*}

这段latex编译报错：
package amsmath error: \hat allowed only in math mode

请问问题出在哪？