I depends a lot on what key you're playing in, but A2 is a good approximation. It isn't A 4, because the 4th of A is D, which is nowhere to be seen--It really isn't technically called a chord unless it has a third interval of some sort in it--we could hedge and call that B a C flat. I guess you could call it an "A double minor". No one would know what you're talking about.

As I think about it, this chord is used in Stephen Schwartz wonderful song, "For Good", from the musical "Wicked". It is called a sus2 chord in the sheet music, which isn't exactly right, because to be a suspended chord, technically, the note has to be suspended over a chord change, and it is arguable whether it does that, but you've got to call it something--Asus2 gets the idea across, anyway--