Anomaly-free dark matter with harmless direct detection constraints

Abstract

Dark matter (DM) interacting with the SM fields via a Z −boson ('Z −portal') remains one of the most attractive WIMP scenarios, both from the theoretical and the phenomenological points of view. In order to avoid the strong constraints from direct detection and dilepton production, it is highly convenient that the Z has axial coupling to DM and leptophobic couplings to the SM particles, respectively. The latter implies that the associated U (1) coincides with baryon number in the SM sector. In this paper we completely classify the possible anomaly-free leptophobic Z with minimal dark sector, including the cases where the coupling to DM is axial. The resulting scenario is very predictive and perfectly viable from the present constraints from DM detection, EW observables and LHC data (di-lepton, di-jet and mono-jet production). We analyze all these constraints, obtaining the allowed areas in the parameter space, which generically prefer m Z < ∼ 500 GeV, apart from resonant regions. The best chances to test these viable areas come from future LHC measurements.

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

“…Refs. [47][48][49]). Here we focus on the contribution of χ to the total decay width of the Z and the resulting interference effects.…”

Multilepton dark matter signals

“…We label the neutral mass eigenstates as N 1,2 and the charged ones as E 1,2 , with masses 3 Without this requirement there is another consistent assignment of ordinary hypercharges in eq. (1), [23]. Hence, the viability of this alternative model requires extra Higgs states in order to present analogous mixing terms.…”

“…Although most of the analyses of these models have been done in the context of simplified dark matter models (SDMM), in which the DM particle, χ, and the mediator, Z ′ , are the only extra fields (see e.g. [22]), it has been recently stressed [3,10,20,23,24] that the ultraviolet (UV) completion of the model requires the presence of additional fields in the dark sector. Such UV completion is enormously simpler and more natural if the axial coupling of the Z ′ boson is to the DM particle, not to the quarks [24].…”

“…There are many possible assignments of the extra hypercharges in the dark sector consistent with anomaly cancellation, but only a few leading to axial Z ′ coupling of χ [8,20,23]. Among them, there is essentially only one in which a unique scalar gives mass not only to the Z ′ boson, but also to all particles in the dark sector, and avoids the presence of electrically charged stable particles [23].…”

“…A preliminary analysis was performed in ref. [23], assuming that the extra dark particles, ψ, η, were very massive, so that they decouple, leading to an effective SDMM (with a fixed correlation between the Z ′ couplings to DM and SM). 1 However, since both the DM particle, χ, and the dark 'leptons', ψ, η, obtain their masses from the same S-VEV, it is natural to assume that these are of the same order.…”