[Xy-pic] Loop arrow in xymatrix?

[Vadim Yu. Radionov]

Dear list members,

Can you help me to draw loop arrow in xymatrix?
I found \ar@(r,dr) in the manual, but i failed to specify directions
different from <diag>, and such arrow touches the horisontal or the
vertical one.  I also tried curve extension, but failed to drop the tip at
the curve's end.

What is the answer?

Sincerely yours,

Vadim

PS. Here are my own ineffectual efforts:

\usepackage[matrix,arrow,curve,dvips]{xy}

\xymatrix@=1.5pc{ & k \ar[d] \\
A\otimes A \ar[r]^-\mu &  A
\curve{"2,2"+(10,-3)&"2,2"+(3,-10)}
\ar@(r,dr)@<-2pt>  \ar[d] \ar[r]^-\Delta &  A\otimes A\rlap. \\
 & k}