Interference effects in dilepton resonance searches for Z′ bosons and dark matter mediators

New Z' gauge bosons arise in many extensions of the Standard Model and predict resonances in the dilepton invariant mass spectrum. Searches for such resonances therefore provide important constraints on many models of new physics, but the resulting bounds are often calculated without interference effects. In this work we show that the effect of interference is significant and cannot be neglected whenever the Z' width is large (for example because of an invisible contribution). To illustrate this point, we implement and validate the most recent 139 fb$^{-1}$ dilepton search from ATLAS and obtain exclusion limits on general Z' models as well as on simplified dark matter models with spin-1 mediators. We find that interference can substantially strengthen the bound on the Z' couplings and push exclusion limits for dark matter simplified models to higher values of the Z' mass. Together with this study we release the open-source code ZPEED, which provides fast likelihoods and exclusion bounds for general Z' models.Comment: v2 matches version accepted by JHEP. 14 pages + appendices, 9 figures + 1 table, ZPEED code to calculate dilepton likelihoods available at http://github.com/kahlhoefer/ZPEE

Strongly interacting dark sectors in the early Universe and at the LHC through a simplified portal

We study the cosmology and LHC phenomenology of a consistent strongly interacting dark sector coupled to Standard Model particles through a generic vector mediator. We lay out the requirements for the model to be cosmologically viable, identify annihilations into dark vector mesons as the dominant dark matter freeze-out process and discuss bounds from direct detection. At the LHC the model predicts dark showers, which can give rise to semi-visible jets or displaced vertices. Existing searches for di-jet resonances and for missing energy mostly probe the parameter regions where prompt decays are expected and constrain our model despite not being optimised for dark showers. We also estimate the sensitivity of dedicated analyses for semi-visible jets and emphasize the complementarity of different search strategies.Comment: 28 pages, 8 figures; v2 matches published versio

Erratum to: Axion global fits with Peccei-Quinn symmetry breaking before inflation using GAMBIT

Example for the effect of wrongly defining the axion-photon coupling. The colour map and black lines are for the corrected figure using GAMBIT 1.3.1, while dashed blue lines indicate the previous erroneous exclusion lines from GAMBIT 13 0