  Neutral diboson processes are precise probes of the Standard Model (SM) of
particle physics, which entail high sensitivity to new physics effects. We
identify in terms of dimension-8 effective operators the leading departures
from the SM that survive in neutral diboson processes at high-energy, and which
interfere with the unsuppressed SM helicity contributions. We describe
symmetries and selections rules that single out those operators, both for
weakly and strongly coupled physics beyond the SM. Finally, we show that
unitarity and causality enforce, via dispersion relations, positivity
constraints on the coefficients of these effective operators, reducing the
parameter space which is theoretically allowed.
