Speaker
Description
We conduct a combined analysis to investigate dark matter (DM) with hypercharge anapole
moments, focusing on scenarios where Majorana DM particles with spin 1/2 or 1 interact
exclusively with Standard Model particles through U(1)Y hypercharge anapole terms. For
completeness, we construct general, effective, and hypercharge gauge-invariant three-point
vertices. These enable the generation of interaction vertices for both a virtual photon γ and
a virtual Z boson with two identical massive Majorana particles of any non-zero spin s, after
the spontaneous breaking of electroweak gauge symmetry. For complementarity, we adopt an
effective operator tailored to each dark matter spin allowing crossing symmetry. We calculate
the relic abundance, analyze current constraints and future sensitivities from dark matter
direct detection and collider experiments, and apply the conceptual naive perturbativity
bound. Our findings demonstrate that the scenario with spin-1 DM is more stringently
constrained than that with spin-1/2, primarily due to the reduced annihilation cross-section
and/or the enhanced rate of LHC mono-jet events. A significant portion of the remaining
parameter space in the spin-1/2 DM scenario can be explored through upcoming Xenon
experiments, with more than 20 ton-year exposure equivalent to approximately 5 years of
running the XENONnT experiment. The spin-1 scenario can be almost entirely tested after
the full run of the high-luminosity LHC, except for a very small parameter region where the
DM mass is around 1 TeV. Our estimations, based on a generalized vertex, anticipate even
stronger bounds and sensitivities for Majorana dark matter with higher spins.
