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We explore the phenomenology of Kaluza-Klein (KK) dark matter in very general models with universal extra dimensions (UEDs), emphasizing the complementarity between high-energy colliders and dark matter direct detection experiments. In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UEDs provide a natural framework for such mass degeneracies. We consider both 5-dimensional and 6-dimensional non-minimal UED models, and discuss the detection prospects for various KK dark matter candidates: the KK photon $gamma_1$, the KK $Z$-boson $Z_1$, the KK Higgs boson $H_1$ and the spinless KK photon $gamma_H$. We combine collider limits such as electroweak precision data and expected LHC reach, with cosmological constraints from WMAP, and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, we show that neither colliders, nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions, and the combination of the two types of constraints can be quite powerful. For example, in the case of $gamma_1$ in 5D UEDs the relevant parameter space will be almost completely covered by the combined LHC and direct detection sensitivities expected in the near future.
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We present updated results on the complementarity between high-energy colliders and dark matter direct detection experiments in the context of Universal Extra Dimensions (UED). In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UED provide a natural framework to study such mass degeneracies. We discuss the detection prospects for the KK photon $gamma_1$ and the KK $Z$-boson $Z_1$, combining the expected LHC reach with cosmological constraints from WMAP/Planck, and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, neither colliders, nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions, and the combination of the two types of constraints can be quite powerful.
We explore the phenomenology of Kaluza-Klein (KK) dark matter in very general models with universal extra dimensions (UEDs), emphasizing the complementarity between high-energy colliders and dark matter direct detection experiments. In models with relatively small mass splittings between the dark matter candidate and the rest of the (colored) spectrum, the collider sensitivity is diminished, but direct detection rates are enhanced. UEDs provide a natural framework for such mass degeneracies. We consider both 5-dimensional and 6-dimensional non-minimal UED models, and discuss the detection prospects for various KK dark matter candidates: the KK photon gamma_1 (5D) the KK Z-boson Z_1 (5D) and the spinless KK photon gamma_H (6D). We combine collider limits such as electroweak precision data and expected LHC reach, with cosmological constraints from WMAP and the sensitivity of current or planned direct detection experiments. Allowing for general mass splittings, we show that neither colliders, nor direct detection experiments by themselves can explore all of the relevant KK dark matter parameter space. Nevertheless, they probe different parameter space regions and the combination of the two types of constraints can be quite powerful. For example, in the case of gamma_1 in 5D UEDs the relevant parameter space will be almost completely covered by the combined LHC and direct detection sensitivities expected in the near future.
In Universal Extra Dimension models, the lightest Kaluza-Klein (KK) particle is generically the first KK excitation of the photon and can be stable, serving as particle dark matter. We calculate the thermal relic abundance of the KK photon for a general mass spectrum of KK excitations including full coannihilation effects with all (level one) KK excitations. We find that including coannihilation can significantly change the relic abundance when the coannihilating particles are within about 20% of the mass of the KK photon. Matching the relic abundance with cosmological data, we find the mass range of the KK photon is much wider than previously found, up to about 2 TeV if the masses of the strongly interacting level one KK particles are within five percent of the mass of the KK photon. We also find cases where several coannihilation channels compete (constructively and destructively) with one another. The lower bound on the KK photon mass, about 540 GeV when just right-handed KK leptons coannihilate with the KK photon, relaxes upward by several hundred GeV when coannihilation with electroweak KK gauge bosons of the same mass is included.
We explore the relationship between randomness and nonlocality based on arguments which demonstrate nonlocality without requiring Bell-type inequalities, such as using Hardy relations and its variant like Cabello-Liang (CL) relations. We first clarify the way these relations enable certification of Genuine Randomness (GR) based on the No-signalling principle. Subsequently, corresponding to a given amount of nonlocality, using the relevant quantifier of GR, we demonstrate the following results: (a) We show that in the 2-2-2 scenario, it is possible to achieve close to the theoretical maximum value of 2 bits amount of GR using CL relations. Importantly, this maximum value is achieved using pure non-maximally entangled states for the measurement settings entailing small amount of nonlocality. Thus, this illustrates quantitative incommensurability between maximum achievable certified randomness, nonlocality and entanglement in the same testable context. (b) We also obtain the device-independent guaranteed amount of GR based on Hardy and CL relations, taking into account the effect of varying preparation procedure which is necessary for ensuring the desired security in this case against adversarial guessing attack. This result is compared with that obtained earlier for the Bell-CHSH case. We find that the monotonicity between such guaranteed randomness and nonlocality persists for the Hardy/CL like for Bell-CHSH inequality, thereby showing commensurability between guaranteed randomness and nonlocality, in contrast to the case of maximum achievable randomness. The results of this combined study of maximum achievable as well as guaranteed amounts of GR, obtained for both fixed and varying preparation procedures, demonstrate that the nature of quantitative relationship between randomness and nonlocality is crucially dependent on which aspect (guaranteed/maximum amount) of GR is considered.
Stable massless wormholes are theoretically interesting in their own right as well as for astrophysical applications, especially as galactic halo objects. Therefore, the study of gravitational lensing observables for such objects is of importance, and we do here by applying the parametric post-Newtonian method of Keeton and Petters to massless dyonic charged wormholes of the Einstein-Maxwell-Dilaton field theory and to the massless Ellis wormhole of the Einstein minimally coupled scalar field theory. The paper exemplifies how the lensing signatures of two different solutions belonging to two different theories could be qualitatively similar from the observational point of view. Quantitative differences appear depending on the parameter values. Surprisingly, there appears an unexpected divergence in the correction to differential time delay, which seems to call for a review of its original derivation.
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