  We analyse the real part of one-loop five-parton amplitudes in the
next-to-multi-Regge kinematic (NMRK) limit, to leading power, and to finite
order in the dimensional regularisation parameter. To leading logarithmic (LL)
accuracy, it is known that five-parton amplitudes in this limit are given to
all-orders by a single factorised expression, in which the pair of partons
which are not well-separated in rapidity are described by a two-parton emission
vertex. In this study, we investigate the one-loop amplitudes at
next-to-leading logarithmic (NLL) accuracy, and find that is has a more complex
structure. In particular, it is found that the purely gluonic amplitudes are
compatible with an analogous factorisation of individual colour structures.
From the one-loop amplitudes we extract one-loop two-parton emission vertices,
which are functions of a subset of the momenta of the amplitude. In the
multi-Regge kinematic (MRK) limit, the vertices themselves factorise into the
known one-loop single-parton emission vertices and Lipatov vertex, with
rapidity dependence governed by the one-loop gluon Regge trajectory, as
required by compatibility with the known MRK limit of amplitudes. The one-loop
two-parton emission vertices are necessary ingredients for the construction of
the next-to-next-to leading order (NNLO) jet impact factors in the BFKL
framework.
