Sensitivities and synergies of DUNE and T2HK

Long-baseline neutrino oscillation experiments, in particular the Deep Underground Neutrino Experiment (DUNE) and Tokai to Hyper-Kamiokande (T2HK), will lead the effort in the precision determination of the as yet unknown parameters of the leptonic mixing matrix. In this article, we revisit the potential of DUNE, T2HK and their combination in light of the most recent experimental information. As well as addressing more conventional questions, we pay particular attention to the attainable precision on delta, which is playing an increasingly important role in the physics case of the long-baseline program. We analyze the complementarity of the two designs, identify the benefit of a program comprising distinct experiments and consider how best to optimize the global oscillation program. This latter question is particularly pertinent in light of a number of alternative design options which have recently been mooted: a Korean second detector for T2HK and different beams options at DUNE. We study the impact of these options and quantify the synergies between alternative proposals, identifying the best means of furthering our knowledge of the fundamental physics of neutrino oscillation.