Abstract
Weak vector boson scattering (VBS) is a sensitive probe of new physics effects in the electroweak symmetry breaking. Currently, experimental results at the LHC are interpreted in the effective field theory approach, where possible deviations from the Standard Model in the quartic-gauge-boson couplings are often described by 18 dimension-8 operators. By assuming that a UV completion exists, we derive a new set of theoretical constraints on the coefficients of these operators, i.e. certain combinations of coefficients must be positive. These constraints imply that the current effective approach to VBS has a large redundancy: only about $2\%$ of the full parameter space leads to a UV completion. By excluding the remaining unphysical region of the parameter space, these constraints provide guidance for future VBS studies and measurements.
Highlights
After the discovery of the Higgs boson [1,2], the focus of particle physics has turned to the mechanism of electroweak symmetry breaking and beyond
vector boson scattering (VBS) processes at the Large Hadron Collider (LHC) can be embedded in partonic processes qq → VVqq, where q is a light quark
VBS processes at the LHC and future colliders are among the most important measurements that probe the mechanism of electroweak symmetry breaking
Summary
After the discovery of the Higgs boson [1,2], the focus of particle physics has turned to the mechanism of electroweak symmetry breaking and beyond. Deviations in QGC independent of TGC are captured by 18 dimension-eight effective operators, assuming that TGC and Higgs couplings are constrained by other processes with better experimental accuracies, such as diboson and Higgs on-shell measurements With this assumption, VBS measurements at the LHC have been conveniently interpreted as constraints on these operator coefficients; see, for example, [6,7,8,9,10] for some recent results, and [11] for a compilation of existing experimental limits on QGC coefficients. Based only on the most fundamental principles of quantum field theory, they are general and model independent They have strong impacts: the currently allowed parameter space spanned by 18 dimension-eight coefficients will be drastically reduced, by almost 2 orders of magnitude in volume. If the experiments observed a parameter region that violates the positivity bounds, it would be a very clear sign of violation of the cherished fundamental principles of modern physics
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