  We use the Boer-Mulders functions parameterized from unpolarized $p+D$
Drell-Yan data by the FNAL E866/NuSea Collaboration combined with recently
extracted Collins functions to calculate the $\cos 2 \phi$ asymmetries in
unpolarized semi-inclusive deeply inelastic scattering (SIDIS) processes both
for ZEUS at Hadron Electron Ring Accelerator (HERA) and Jefferson Lab
experiments (JLab), and to compare our results with their data. We also give
predictions for the $\cos 2 \phi$ asymmetries of SIDIS in the kinematical
regime of HERMES Collaboration, and the forthcoming JLab experiments. We
predict that the $\cos 2 \phi$ asymmetries of semi-inclusive $\pi^-$ production
are somewhat larger than that of $\pi^+$ production. We suggest to measure
these two processes separately, which will provide more detail information on
the Boer-Mulders functions as well as on the Collins functions.
