How to execute a command in tmux and detach using a single line command?

How can I get tmux to execute a command and then detach (That is, automatically in a single line without further input beyond initially starting the session)? I don't know to write sophisticated scripts. But I used to do this in screen with a command like:

-S torrent -d -m qbittorrent-nox

But I have been reading that tmux is better and I would like to switch. But I couldn't figure out how to achieve what the above command does.