We investigate the non-relativistic reduction of simplified models for spin 1 dark matter (DM) with the aim of identifying features in the phenomenology of DM-quark interactions which are specific to vector DM. In the case of DM-quark interactions mediated by a spin 1 particle, we find two DM-nucleon interaction operators arising from the nonrelativistic reduction of simplified models for spin 1 DM that are specific to spin 1 DM, and which were not considered in previous studies. They are quadratic in the momentum transfer, linear in a symmetric combination of polarisation vectors for the DM particle, and arise from simplified models which do not generate momentum transfer independent operators as leading interactions in the non-relativistic expansion of DM-nucleon scattering amplitudes. Within these simplified models, the new operators cannot be neglected when computing DM signals at direct detection experiments. For example, we find that nuclear recoil energy spectra computed by including or neglecting the new operators can differ by up to one order of magnitude for nuclear recoil energies larger than about 20 keV and DM masses below 50 GeV. Furthermore, the shape of the expected nuclear recoil spectra depends significantly on whether the new operators are taken into account or not. Finally, neglecting the contribution to DM direct detection signals from the new operators leads to inaccurate conclusions when assessing the compatibility of a future direct detection signal with CMB constraints on the DM relic density, especially when the number of signal events is small, e.g. O(1).

We develop a method to forecast the outcome of the LHC Run 3 based on the hypothetical detection of Oð100Þ signal events at XENONnT. Our method relies on a systematic classification of renormalizable single-mediator models for dark matter-quark interactions and is valid for dark matter candidates of spin less than or equal to one. Applying our method to simulated data, we find that at the end of the LHC Run 3 only two mutually exclusive scenarios would be compatible with the detection of Oð100Þ signal events at XENONnT. In the first scenario, the energy distribution of the signal events is featureless, as for canonical spin-independent interactions. In this case, if a monojet signal is detected at the LHC, dark matter must have spin 1=2 and interact with nucleons through a unique velocity-dependent operator. If a monojet signal is not detected, dark matter interacts with nucleons through canonical spin-independent interactions. In a second scenario, the spectral distribution of the signal events exhibits a bump at nonzero recoil energies. In this second case, a monojet signal can be detected at the LHC Run 3; dark matter must have spin 1=2 and interact with nucleons through a unique momentum-dependent operator. We therefore conclude that the observation of Oð100Þ signal events at XENONnT combined with the detection, or the lack of detection, of a monojet signal at the LHC Run 3 would significantly narrow the range of possible dark matter-nucleon interactions. As we argued above, it can also provide key information on the dark matter particle spin.

SO(10) grand unified theories can ensure the stability of new particles in terms of the gauge group structure itself, and in this respect are well suited to accommodate dark matter (DM) candidates in the form of new stable massive particles. We introduce new fermions in two vector 10 representations. When SO (10) is broken to the standard model by a minimal 45 + 126 + 10 scalar sector with SUas intermediate symmetry group , the resulting lightest new states are two Dirac fermions corresponding to combinations of the neutral members of the SU (2) L doublets in the 10's, which get splitted in mass by loop corrections involving W R . The resulting lighter mass eigenstate is stable, and has only nondiagonal Z L,R neutral current couplings to the heavier neutral state. Direct detection searches are evadedif the mass splitting is sufficiently large to suppress kinematically inelastic light-to-heavy scatterings. By requiring that this condition is satisfied, we obtain the upper limit M W R < ∼ 25 TeV.

The discovery of dark matter (DM) at XENONnT or LZ would place constraints on DM particle mass and coupling constants. It is interesting to ask when these constraints can be compatible with the DM thermal production mechanism. We address this question within the most general set of renormalizable models that preserve Lorentz and gauge symmetry, and that extend the standard model by one DM candidate of mass m DM and one particle of mass M med mediating DM-quark interactions. Our analysis divides into two parts. First, we postulate that XENONnT/LZ has detected μ S ∼ Oð100Þ signal events, and use this input to calculate the DM relic density, Ω DM h 2 . Then, we identify the regions in the M med − Ω DM h 2 plane which are compatible with the observed signal and with current CMB data. We find that for most of the models considered here, Oð100Þ signal events at XENONnT/LZ and the DM thermal production are only compatible for resonant DM annihilations, i.e. for M med ≃ 2m DM . In this case, XENONnT/LZ would be able to simultaneously measure m DM and M med . We also discuss the dependence of our results on m DM , μ S and the DM spin, and provide analytic expressions for annihilation cross sections and mediator decay widths for all models considered in this study.

If the dark matter particle has spin 0, only two types of WIMP-nucleon interaction can arise from the non-relativistic reduction of renormalisable single-mediator models for dark matter-quark interactions. Based on this crucial observation, we show that about 100 signal events at next generation directional detection experiments can be enough to enable a 2σ rejection of the spin 0 dark matter hypothesis in favour of alternative hypotheses where the dark matter particle has spin 1/2 or 1. In this context directional sensitivity is crucial, since anisotropy patterns in the sphere of nuclear recoil directions depend on the spin of the dark matter particle. For comparison, about 100 signal events are expected in a CF4 detector operating at a pressure of 30 torr with an exposure of approximately 26,000 cubic-meter-detector days for WIMPs of 100 GeV mass and a WIMP-Fluorine scattering cross-section of 0.25 pb. Comparable exposures are within reach of an array of cubic meter time projection chamber detectors. lite [7]. Finally, the best direct-detection constraints on spin-dependent WIMP-proton and WIMP-neutron scattering cross-sections have been derived by and LUX [9], respectively.