Wenger argued furiously with Busacca on the sidelines after Arsenal’s 3-1 loss Tuesday, and the dispute continued in the tunnel. Arsenal lost 4-3 on aggregate.
Wenger was angry that forward Robin van Persie was shown a second yellow card at 1-1 in the 56th minute.
Busacca ruled that Van Persie deliberately kicked the ball away when shooting after being ruled offside.
UEFA studied reports from Busacca and match delegate Dane Jost before asking its disciplinary unit to investigate.