The Standard Model effective field theory (SMEFT) provides a robust framework for probing deviations in the couplings of Standard Model particles from their theoretical predictions. This framework relies on an expansion in higher-dimensional operators, often truncated at dimension-six. In this work, we compute the effective dimension-eight operators generated by integrating out heavy scalar fields at one-loop order in the Green’s basis within two extended scalar sector models: the two Higgs doublet model and the complex triplet scalar model. In this work, we consider loops that consist of heavy field propagators only. We also investigate the impact of heavy scalar fields on the fermion sector, deriving the fermionic effective operators up to dimension-eight for these models, and detail how contributions can be mapped onto nonredundant bases. To assess the importance of higher-order contributions in the SMEFT expansion, we analyze dimension-eight effects for electroweak precision observables at the next frontier of precision lepton machines such as GigaZ.

We present constraints on low-mass dark matter electron scattering and absorption interactions using a SuperCDMS high-voltage eV-resolution (HVeV) detector. Data were taken underground in the NEXUS facility located at Fermilab with an overburden of 225 meters of water equivalent. The experiment benefits from the minimizing of luminescence from the printed circuit boards in the detector holder used in all previous HVeV studies. A blind analysis of 6.1 g · days of exposure produces exclusion limits for dark matter-electron scattering cross sections for masses as low as 1 MeV / c 2 , as well as on the photon-dark photon mixing parameter and the coupling constant between axionlike particles and electrons for particles with masses > 1.2 eV / c 2 probed via absorption processes.

This work investigates the prospects for performing a time-dependent angular analysis of B s 0 → ϕ μ + μ − decays at hadron colliders, and introduces new optimized angular observables associated with B s 0 -mixing in the decay rate. The time-dependent normalized decay rate and corresponding probability density function is presented both for when the flavor of the B s 0 meson at production is tagged and when it is untagged. The normalized angular terms linked to B s 0 -mixing in the tagged (untagged) case are denoted Z i ( H i ), and their optimized counterparts as Q i ( M i ). The expected sensitivities of these observables at the end of Run 3, Run 4, and Run 5 of the LHC are determined using pseudoexperiments generated with a decay-time resolution, background level, and signal yield similar to those reported by the LHCb Collaboration. It is found that all observables can be extracted with Run 3 statistics, and that the H i and Z i observables have similar sensitivity, despite the former being suppressed by mixing terms. Moreover, the angular observables only accessible via flavor tagging, such as the equivalent of P 5 ′ in the B s 0 system, are found to exhibit sensitivities comparable to current measurements in B 0 → K * 0 μ + μ − decays once Run 5 datasets are available. Fits to the observables to extract the Wilson coefficients show a significant increase in precision when either the observables accessible via time-dependent analysis, or flavor tagging, are included. A marked increase in sensitivity to C P -violating short-distance effects is observed for a subset of the new optimized M i and Q i observables.

Axion dark matter passing through the magnetospheres of magnetars can undergo hyperefficient resonant mixing with low-energy photons, leading to the production of narrow spectral lines that could be detectable on Earth. Since this is a resonant process triggered by the spatial variation in the photon dispersion relation, the luminosity and spectral properties of the emission are highly sensitive to the charge and current densities permeating the magnetosphere. To date, a majority of the studies investigating this phenomenon have assumed a perfectly dipolar magnetic field structure with a near-field plasma distribution fixed to the minimal charge-separated force-free configuration. While this may be a reasonable treatment for the closed field lines of conventional radio pulsars, the strong magnetic fields around magnetars are believed to host processes that drive strong deviations from this minimal configuration. In this work, we study how realistic magnetar magnetospheres impact the electromagnetic emission produced from axion dark matter. Specifically, we construct charge and current distributions that are consistent with magnetar observations and use these to recompute the prospective sensitivity of radio and submillimeter telescopes to axion dark matter. We demonstrate that the two leading models yield vastly different predictions for the frequency and amplitude of the spectral line, indicating systematic uncertainties in the plasma structure are significant. Finally, we discuss various observational signatures that can be used to differentiate the local plasma loading mechanism of an individual magnetar, which will be necessary if there is hope of using such objects to search for axions.