Anatomy of inclusive t(t)over-barW production at hadron colliders

In LHC searches for new and rare phenomena the top-associated channel pp -> t (t) over barW(+/-) + X is a challenging background that multilepton analyses must overcome. Motivated by sustained measurements of enhanced rates of same-sign and multi-lepton final states, we reexamine the importance of higher jet multiplicities in pp -> t (t) over barW(+/-) + X that enter at O(alpha(3)(s)alpha) and O(alpha(4)(s)alpha), i.e., that contribute at NLO and NNLO in QCD in inclusive t (t) over barW(+/-) production. Using fixed-order computations, we estimate that a mixture of real and virtual corrections at O(alpha(4)(s)alpha) in well-defined regions of phase space can arguably increase the total t (t) over barW(+/-) rate at NLO by at least 10% - 14%. However, by using non-unitary NLO multi-jet matching, we estimate that these same corrections are at most 10% - 12%, and at the same time exhibit the enhanced jet multiplicities that are slightly favored by data. This seeming incongruity suggests a need for the full NNLO result. We comment on implications for the t (t) over barZ process. (C) 2020 The Author(s). Published by Elsevier B.V.