We calculated the color-octet contribution to the double spin asymmetry of
J/ψ hadroproduction with nonzero transverse momenta at fixed target
energies s≃40 GeV. It is shown that the color-octet contribution
is dominant in the asymmetries. The expected asymmetries and statistical errors
in a future option of HERA with longitudinally polarized protons at HERA-N should allow one to distinguish between different parametrizations for the
polarized gluon distribution in the proton.Comment: 14 pages with 6 figures (epsfig), LaTeX; Some figures are changed and
misprint is correcte