Precision diboson observables for the LHC

Motivated by the restoration of su(2) × u(1) at high energy, we suggest that certain ratios of diboson differential cross sections can be used as high-precision observables at the lhc. we rewrite leading-order diboson partonic cross sections in a form that makes their su(2) × u(1) and custodial su(2) structure more explicit than in previous literature, and identify important aspects of this structure that survive even in hadronic cross sections. we then focus on higher-order corrections to ratios of γγ, zγ and zz processes, including full next-to-leading-order corrections and gg initial-state contributions, and argue that these ratios can likely be predicted to better than 5%, which should make them useful in searches for new phenomena. the ratio of zγ to γγ is especially promising in the near term, due to large rates and to exceptional cancellations of qcd-related uncertainties. we argue that electroweak corrections are moderate in size, have small uncertainties, and can potentially be observed in these ratios in the long run.