\section{Results and discussions}
\subsection{Titanium}
Number of stopped muons in the natural titanium target was:
\begin{equation}
  N_{\mu} = (88296 \pm 9) \times 10^3 \,.
  \label{eqn:Nmu_Ti_Tsc}
\end{equation}

Fitting the peak around \SI{931}{keV} in the photon spectrum gives the 
center of gravity at \SI{931.6 \pm 0.7}{keV} (see~\cref{fig:ti_931keV_fit}),
consistent with previously reported value~\cite{Wohlfahrt1981}.
Number of $(2p-1s)$ X-rays in the \SI{931.6}{keV} peak is:
\begin{equation}
  N_{931.6} = (20750 \pm 764) \,.
\end{equation}

\begin{figure}[tbp]
  \centering
  \includegraphics[width=0.8\textwidth]{figs/ti_931keV_fit}
  \caption{Fitting $(2p-1s)$ peaks on \ce{^{nat}Ti}}
  \label{fig:ti_931keV_fit}
\end{figure}

The emission rate of the $(2p-1s)$ muonic X-rays is calculated as:
\begin{equation}
  R_{Ti} = \frac{N_{931.6}}{A_{931.6} \times N_{\mu} \times f_{capTi}} = 0.90
  \pm 0.04 \,.
\end{equation}