$J/\psi$ Spin Alignment in $p \overline{p}$ Collisions at $\sqrt{s} = 1.96$ TeV

We have measured the spin alignment of prompt $J/\psi$ mesons produced in $p\overline{p}$ collisions at $\sqrt{s}=1.96 {\rm TeV}$ using data collected by CDF II detector. The $J/\psi$ mesons are reconstructed by $J/\psi\rightarrow\mu\mu$ decays and promptly produced $J/\psi$ mesons are separated from those produced in $B$-hadron decay using the impact parameter information of muons. The polarization is measured over the kinematic range $4