  We calculate the transverse momentum dependent gluon-to-gluon splitting
function within kT-factorization [EPJC 78 (2018) 174], generalizing the
framework of [NPB 175 (1980) 27; NPB 427 (1994) 475] and extending our previous
works [JHEP 01 (2016) 181; PRD 94 (2016) 114013] for the quark splittings.
While existing versions of kT factorized evolution equations contain already a
gluon-to-gluon splitting function i.e. the leading order BFKL kernel or the
CCFM kernel, the obtained splitting function has the important property that it
reduces to the leading order BFKL kernel in the low z limit, to the DGLAP
gluon-to-gluon splitting function in the collinear limit as well as to the CCFM
kernel in the angular ordered region.
