
\documentclass[border=5pt,multi=true]{standalone}
\usepackage{standalone}
\usepackage{ifthen}
\usepackage{rotating}
\usepackage{graphpap}
\usepackage{multirow}
\usepackage{mathrsfs}
\usepackage{pifont}
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\usepackage{microtype}
\usepackage{lineno}
\usepackage{xspace}
\usepackage{caption}
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\usepackage{hyperref}
\usepackage{hypcap}
\usepackage{cite}
\usepackage{mciteplus}
\usepackage{longtable}


\graphicspath{{./figs/}}

\begin{document}
\DeclareGraphicsExtensions{.pdf}
\setlength{\unitlength}{1mm}
  \centering
  \begin{picture}(150,60)
    \put(  0,  0){
      \includegraphics*[width=75mm,height=60mm,%
      ]{Fig2a.pdf}
    }
    \put( 75,  0){
      \includegraphics*[width=75mm,height=60mm,%
      ]{Fig2b.pdf}
    }
     \put ( 40, 30) { \small
        $\begin{array}{l}
        {\color{blue}       \square}~~\ensuremath{\ensuremath{\ensuremath{B}\xspace}\xspace^+}\xspace\ensuremath{\rightarrow}\xspace\ensuremath{{\ensuremath{J}\xspace\mskip -3mu/\mskip -2mu\ensuremath{\psi}\xspace\mskip 2mu}}\xspace\ensuremath{\ensuremath{\ensuremath{K}\xspace}\xspace^+}\xspace  \\
        {\color{red} \text{\ding{108}}}~~\ensuremath{\ensuremath{\ensuremath{B}\xspace}\xspace_\ensuremath{\ensuremath{c}\xspace}\xspace^+}\xspace\ensuremath{\rightarrow}\xspace\ensuremath{{\ensuremath{J}\xspace\mskip -3mu/\mskip -2mu\ensuremath{\psi}\xspace\mskip 2mu}}\xspace\ensuremath{\ensuremath{\ensuremath{\pi}\xspace}\xspace^+}\xspace        
    \end{array}$}                                      
    \put( 20, 50) {a)}
    \put( 55, 50) {LHCb}
    \put(  0, 30) {\begin{sideways}$\frac{\mathop{}\!\mathrm{d} N_{\ensuremath{\ensuremath{B}\xspace}\xspace}}{\mathop{}\!\mathrm{d} t}~~~~\left[\frac{1}{25\ensuremath{{\,\upmu\rm m}}\xspace/c}\right]$\end{sideways} }
    \put( 40,  0) { $t$ }
    \put( 59,  0) { $\left[\!\ensuremath{\rm \,mm}\xspace/{\mathit{c}}\right]$ }
    \put( 95, 50) {b)}
    \put(110, 50) {LHCb simulation}
    \put( 75, 46){ \begin{sideways}$\mathcal{R}_{\varepsilon}(t)$\end{sideways} }
    \put(115,  0) { $t$ }
    \put(134,  0) { $\left[\!\ensuremath{\rm \,mm}\xspace/{\mathit{c}}\right]$ }
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\end{document}
