  The use of Terahertz (THz) frequency bands for data transmissions between the
core network and an access point can be promising for next generation wireless
systems. In this paper, we analyze the performance of a dual-hop relaying for
THz-RF wireless link for backhaul applications. Considering the $\alpha-\mu$
fading channel and a statistical model of pointing errors, we derive a novel
closed-form expression of the cumulative distribution function (CDF) of the
signal-to-noise ratio (SNR) for the THz link, which is also valid for
non-integer values of $\mu$. Using the CDF, we derive analytical expressions of
the end-to-end SNR and lower bound on ergodic capacity of a decode-and-forward
(DF) assisted THz-RF relaying in terms of system parameters. Using analytical
results of the direct link and computer simulations, we demonstrate that the
THz-RF relaying is a viable technology for wireless backhaul, providing a
significant increase of almost $25 \%$ in the spectral efficiency, compared to
the direct transmissions.
