Non--global logs and clustering impact on jet mass with a jet veto distribution

Abstract

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.