The symbol separating the dividend from the divisor in a long division that is drawn as a right parenthesis (or sometimes a straight vertical bar) with an attached vinculum extending to the right seems to have no established name of its own. It can therefore simply be termed the "long division symbol," or sometimes the division bracket.

 

Dividend, Division, Divisor, Long Division, Obelus, Solidus, Vinculum, Virgule