We propose and experimentally demonstrate a method for detection of light scalar Dark Matter (DM), through probing temporal oscillations of fundamental constants in an atomic optical transition. Utilizing the quantum information notion of Dynamic Decoupling (DD) in a table-top setting, we are able to obtain model-independent bounds on variations of α and me at frequencies up to the MHz scale. We interpret our results to constrain the parameter space of light scalar DM field models. We consider the generic case, where the couplings of the DM field to the photon and to the electron are independent, as well as the case of a relaxion DM model, including the scenario of a DM boson star centered around Earth.Given the particular nature of DD, allowing to directly observe the oscillatory behaviour of coherent DM, and considering future experimental improvements, we conclude that our proposed method could be complimentary to, and possibly competitive with, gravitational probes of light scalar DM.

Colored and colorless particles that are stable on collider scales and carry exotic electric charges, so-called multiply-charged heavy stable particles (MCHSPs), exist in extensions of the Standard Model, and can include the top partner(s) in solutions of the hierarchy problem. To obtain bounds on color-triplets and color-singlets of charges up to |Q| = 8, we recast searches for signatures of two production channels: the "open" channel -where the particles are pair-produced above threshold, and are detectable in dedicated LHC searches for stable multiply charged leptons, and the "closed" channel -where a particle-antiparticle pair is produced as a bound state, detectable in searches for a diphoton resonance. We recast the open lepton searches by incorporating the relevant strong-interaction effects for color-triplets. In both open and closed production, we provide a careful assessment of photon-induced processes using the accurate LUXqed PDF, resulting in substantially weaker bounds than previously claimed in the literature for the colorless case. Our bounds for colored MCHSPs are shown for the first time, as the LHC experiments have not searched for them directly. Generally, we obtain nearly charge-independent lower mass limits of around 970 GeV (color-triplet scalar), 1200 GeV (color-triplet fermion), and 880 − 900 GeV (color-singlet fermion) from open production, and strongly chargedependent limits from closed production. In all cases there is a cross-over between dominance by open and closed searches at some charge. We provide prospective bounds for √ s = 13 TeV LHC searches at integrated luminosities of 39.5 fb −1 , 100 fb −1 , and 300 fb −1 . Moreover, we show that a joint observation in the open and the closed channels allows to determine the mass, spin, color, and electric charge of the particle.

Spin-0 singlets arise in well-motivated extensions of the Standard Model. Their lifetime determines the best search strategies at hadron and lepton colliders. To cover a large range of singlet decay lengths, we investigate bounds from Higgs decays into a pair of singlets, considering signatures of invisible decays, displaced and delayed jets, and coupling fits of untagged decays. We examine the generic scalar singlet and the relaxion, and derive a matching as well as qualitative differences between them. For each model, we discuss its natural parameter space and the searches probing it.

In this paper we study CP violation in photon self-interactions at low energy. These interactions, mediated by the effective operator $$ FFF\tilde{F} $$ FFF F ˜ , where ($$ \tilde{F} $$ F ˜ ) F is the (dual) electromagnetic field strength, have yet to be directly probed experimentally. Possible sources for such interactions are weakly coupled light scalars with both scalar and pseudoscalar couplings to photons (for instance, complex Higgs-portal scalars or the relaxion), or new light fermions coupled to photons via dipole operators. We propose a method to isolate the CP-violating contribution to the photon self-interactions using Superconducting Radio-Frequency cavities and vacuum birefringence experiments. In addition, we consider several theoretical and experimental indirect bounds on the scale of new physics associated with the above effective operator, and present projections for the sensitivity of the proposed experiments to this scale. We also discuss the implications of these bounds on the CP-violating couplings of new light particles coupled to photons.

The LHCb experiment measured the time-dependent CP asymmetries CKK and SKK in Bs→ K+K− decay. Combining with the corresponding CP asymmetries Cππ and Sππ in B → π+π− decay, we find that the size of U-spin breaking in this system is of order 20%. Moreover, the data suggest that these effects are dominated by factorizable contributions. We further study the constraints on new physics contributions to b →$$ u\overline{u}q $$ u u ¯ q (q = s, d). New physics that is minimally flavor violating (MFV) cannot be distinguished from the Standard Model (SM) in these decays. However, new physics that is not MFV can mimic large U-spin breaking. Requiring that the U-spin breaking parameters remain below the size implied by the data leads to a lower bound of 5 − 10 TeV on the scale of generic new physics. If the new physics is subject to the selection rules that follow from the Froggatt-Nielsen (FN) mechanism or from General Minimal Flavor Violation (GMFV), the bound is relaxed to 2 TeV.