To reproduce the symbol in question exactly, you will need to have access to the MathTime II Professional font package, a commercial Times Roman clone math font. It is not free of charge; however, it's not superexpensive either.
If the following test document compiles successfully on your system, you already have the font.
\documentclass{article}
\usepackage[scr=mt]{mathalfa}
\begin{document}
$\mathscr{S}$
\end{document}

If you don't want to spend the money on a math font package for just one symbol, you could consider replacing \usepackage[scr=mt]{mathalfa} with \usepackage{stix2} -- another Times Roman clone math font package.
\mathcal{S}. It's not a particular symbol, just a script S. – egreg Jul 14 '22 at 10:19