We propose that back-to-back correlations in azimuthal angle of jets produced
in collisions of unpolarized with transversely polarized proton beams could be
used to determine Sivers functions. The corresponding single-spin asymmetry is
not power-suppressed, but is subject to Sudakov suppression. We present
estimates of the asymmetry (without and with Sudakov effects) for RHIC at jet
transverse momenta of ~10 GeV and show that it may reach a few per cent or more
and could provide access to the gluon Sivers function.Comment: 14 pages, LaTeX, 3 figures as epsi files. With minor additions to
first version. Accepted for publication in Phys. Rev.