Effects of a neutrino-dark energy coupling on oscillations of high-energy neutrinos

If dark energy (DE) is a dynamical field rather than a cosmological constant, an interaction between DE and the neutrino sector could exist, modifying the neutrino oscillation phenomenology and causing CP and apparent Lorentz violating effects. The terms in the Hamiltonian for flavor propagation induced by the DE-neutrino coupling do not depend on the neutrino energy, while the ordinary components decrease as $\Delta m^2/E_{\nu}$. Therefore, the DE-induced effects are absent at lower neutrino energies, but become significant at higher energies, allowing to be searched for by neutrino observatories. We explore the impact of the DE-neutrino coupling on the oscillation probability and the flavor transition in the three-flavor framework, and investigate the CP-violating and apparent Lorentz violating effects. We find that DE-induced effects become observable for $E_{\nu}m_{\text{eff}} \sim 10^{-20}~ \text{GeV}^2$, where $m_{\rm eff}$ is the effective mass parameter in the DE-induced oscillation probability, and CP is violated over a wide energy range. We also show that current and future experiments have the sensitivity to detect anomalous effects induced by a DE-neutrino coupling and probe the new mixing parameters. The DE-induced effects on neutrino oscillation can be distinguished from other new physics possibilities with similar effects, through the detection of the directional dependence of the interaction, which is specific to this interaction with DE. However, current experiments will not yet be able to measure the small changes of $\sim 0.03\%$ in the flavor composition due to this directional effect.Comment: 11 pages, 15 figure

Impact of axisymmetric mass models for dwarf spheroidal galaxies on indirect dark matter searches

Dwarf spheroidals are low-luminosity satellite galaxies of the Milky Way highly dominated by dark matter (DM). Therefore, they are prime targets to search for signals from dark matter annihilation using gamma-ray observations. While the typical assumption is that the dark matter density profile of these satellite galaxies can be described by a spherical symmetric Navarro-Frenk-White (NFW) profile, recent observational data of stellar kinematics suggest that the DM halos around these galaxies are better described by axisymmetric profiles. Motivated by such evidence, we analyse about seven years of PASS8 Fermi data for seven classical dwarf galaxies, including Draco, adopting both the widely used NFW profile and observationally-motivated axisymmetric density profiles. For four of the selected dwarfs (Sextans, Carina, Sculptor and Fornax) axisymmetric mass models suggest a cored density profile rather than the commonly adopted cusped profile. We found that upper limits on the annihilation cross section for some of these dwarfs are significantly higher than the ones achieved using an NFW profile. Therefore, upper limits in the literature obtained using spherical symmetric cusped profiles, such as the NFW, might be overestimated. Our results show that it is extremely important to use observationally motivated density profiles going beyond the usually adopted NFW in order to obtain accurate constraints on the dark matter annihilation cross section.Comment: 9 pages, 5 figure

Constraints on MeV dark matter using neutrino detectors and their implication for the 21-cm results

The recent results of the EDGES collaboration indicate that during the era of reionization, the primordial gas was much colder than expected. The cooling of the gas could be explained by interactions between dark matter (DM) and particles in the primordial gas. Constraints from cosmology and particle experiments indicate that this DM should be light ($\sim$10-80 MeV), carry a small charge ($\epsilon\sim 10^{-6}$-$10^{-4}$), and only make up a small fraction of the total amount of DM. Several constraints on the DM parameter space have already been made. We explore the yet unconstrained region in the case that the milli-charged DM makes up for $\sim$2\% of the total dark matter, through the scenario in which this DM annihilates only into mu and tau neutrinos. We set upper limits on the annihilation cross section using the Super-Kamiokande data, and predict the limits that could be obtained through Hyper-Kamiokande, JUNO and DUNE. We find that data from Super-Kamiokande is not yet able to constrain this model, but future experiments might be. We furthermore explore DM annihilation into solely neutrinos in general, giving an update of the current limits, and predict the limits that could be placed with future experiments.Comment: 6 pages, 6 figure