  There has recently been much interest in analytical computations of jet mass
distributions with and without vetos on additional jet activity [1-6]. An
important issue affecting such calculations, particularly at next-to-leading
logarithmic (NLL) accuracy, is that of non-global logarithms as well as
logarithms induced by jet definition, as we pointed out in an earlier work [3].
In this paper, we extend our previous calculations by independently deriving
the full jet-radius analytical form of non-global logarithms, in the anti-$\kt$
jet algorithm. Employing the small-jet radius approximation, we also compute,
at fixed-order, the effect of jet clustering on both $\CF^{2}$ and $\CF\CA$
colour channels. Our findings for the $\CF\CA$ channel confirm earlier
analytical calculations of non-global logarithms in soft-collinear effective
theory [5]. Moreover, all of our results, as well as those of [3], are compared
to the output of the numerical program \texttt{EVENT2}. We find good agreement
between analytical and numerical results both with and without final state
clustering.
