Abstract
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.
Highlights
We identify in terms of dimension-8 effective operators the leading departures from the Standard Model (SM) that survive in neutral diboson processes at high energy and that interfere with the unsuppressed SM helicity contributions
Departures from the SM that are unsuppressed at high energy, and possibly interfere with the SM in simple analyses, have the highest chance of being detected; these are the effects that are most interesting from an experimental perspective
We have provided a parametrization for neutral diboson processes with initial state fermions, which extends the traditional parametrization based on neutral triple gauge couplings
Summary
Standard Model (SM) precision tests constitute an important part of the LHC physics program, in which SM predictions are confronted against precise data from proton-proton collisions. Despite the high dimensionality of the operator, the coefficient cði8Þ can be sizeable in theories with a relatively strong underlying coupling, so much so as to partly alleviate the E=Λ suppression that accompanies the contribution of these operators to physical amplitudes For this reason, we can expect measurable effects even from these higher-dimensional operators. III), we propose a set of operators of this kind This model-independent reasoning will provide an important way to focus experimental searches to a smaller region of parameter space
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