Typically, a production of a particle with a small transverse momentum in hadron-hadron collisions is described
by CSS-based TMD factorization at moderate Bjorken $x_B\sim 1$ and by $k_T$-factorization at small $x_B$.
A uniform description valid for all $x_B$ is provided by rapidity-only TMD factorization developed in a series
of recent papers at the tree level. In this paper the rapidity-only TMD factorization for particle production by
gluon fusion is extended to the one-loop level.