A Possible Detection of the Cosmic Antineutrino Background in the Presence of Flavor Effects

Lusignoli and Vignati have recently pointed out that it is in principle possible to directly detect the cosmic antineutrino background by using the rather stable isotope holmium-163 as a target, which can decay into dysprosium-163 via electron capture (EC) with a very small energy release. In this paper we calculate the rate of the relic antineutrino capture on holmium-163 nuclei against the corresponding EC decay rate by taking account of different neutrino mass hierarchies and reasonable values of theta_13. We show that such flavor effects are appreciable and even important in some cases, and stress that a calorimetric measurement of the cosmic antineutrino background might be feasible in the far future.Comment: 13 pages, 5 figures, revised version, accepted for publication in Phys. Lett.

Possible Capture of keV Sterile Neutrino Dark Matter on Radioactive beta-decaying Nuclei

There exists an observed "desert" spanning six orders of magnitude between O(0.5) eV and O(0.5) MeV in the fermion mass spectrum. We argue that it might accommodate one or more keV sterile neutrinos as a natural candidate for warm dark matter. To illustrate this point of view, we simply assume that there is one keV sterile neutrino nu_4 and its flavor eigenstate nu_s weakly mixes with three active neutrinos. We clarify different active-sterile neutrino mixing factors for the radiative decay of nu_4 and beta decays in a self-consistent parametrization. A direct detection of this keV sterile neutrino dark matter in the laboratory is in principle possible since the nu_4 component of nu_e can leave a distinct imprint on the electron energy spectrum when it is captured on radioactive beta-decaying nuclei. We carry out an analysis of its signatures in the capture reactions nu_e + ^{3}H \to ^{3}He + e^- and nu_e + ^{106}Ru \to ^{106}Rh + e^- against the beta-decay backgrounds, and conclude that this experimental approach might not be hopeless in the long run.Comment: 14 pages, 3 figures, more discussions and references added. To appear in PL

Direct Detection of the Cosmic Neutrino Background Including Light Sterile Neutrinos

Current cosmological data drop an interesting hint about the existence of sub-eV sterile neutrinos, which should be a part of the cosmic neutrino background (C$\nu$B). We point out that such light sterile neutrinos may leave a distinct imprint on the electron energy spectrum in the capture of relic electron neutrinos by means of radioactive beta-decaying nuclei. We examine possible signals of sterile neutrinos relative to active neutrinos, characterized by their masses and sensitive to their number densities, in the reaction $\nu^{}_e + ~^3{\rm H} \to ~^3{\rm He} + e^-$ against the corresponding tritium beta decay. We stress that this kind of direct laboratory detection of the C$\nu$B and its sterile component might not be hopeless in the long term.Comment: Minor changes. Accepted for publication in Phys. Lett.

Modeling realistic Earth matter density for CP violation in neutrino oscillation

We examine the effect of a more realistic Earth matter density model which takes into account of the local density variations along the baseline of a possi ble 2100 km very long baseline neutrino oscillation experiment. Its influence to the measurement of CP violation is investigated and a comparison with the commonly used global density models made. Significant differences are found in the comparison of the results of the different density models.Comment: 16 pages, 8 figure

Vanishing effective mass of the neutrinoless double beta decay including light sterile neutrinos

Light sterile neutrinos with masses at the sub-eV or eV scale are hinted by current experimental and cosmological data. Assuming the Majorana nature of these hypothetical particles, we discuss their effects in the neutrinoless double beta decay by exploring the implications of a vanishing effective Majorana neutrino mass. Allowed ranges of neutrino masses, mixing angles and Majorana CP-violating phases are illustrated in some instructive cases for both normal and inverted mass hierarchies of three active neutrinos.Comment: 14 pages, 4 figures, more discussions and references added, accepted for publication in PL

A White Paper on keV sterile neutrino Dark Matter

We present a comprehensive review of keV-scale sterile neutrino Dark Matter, collecting views and insights from all disciplines involved—cosmology, astrophysics, nuclear, and particle physics—in each case viewed from both theoretical and experimental/observational perspectives. After reviewing the role of active neutrinos in particle physics, astrophysics, and cosmology, we focus on sterile neutrinos in the context of the Dark Matter puzzle. Here, we first review the physics motivation for sterile neutrino Dark Matter, based on challenges and tensions in purely cold Dark Matter scenarios. We then round out the discussion by critically summarizing all known constraints on sterile neutrino Dark Matter arising from astrophysical observations, laboratory experiments, and theoretical considerations. In this context, we provide a balanced discourse on the possibly positive signal from X-ray observations. Another focus of the paper concerns the construction of particle physics models, aiming to explain how sterile neutrinos of keV-scale masses could arise in concrete settings beyond the Standard Model of elementary particle physics. The paper ends with an extensive review of current and future astrophysical and laboratory searches, highlighting new ideas and their experimental challenges, as well as future perspectives for the discovery of sterile neutrinos

Ebullition was a major pathway of methane emissions from the aquaculture ponds in southeast China

Aquaculture ponds are hotspots of carbon cycling and important anthropogenic sources of the potent greenhouse gas methane (CH4). Despite the importance of CH4 ebullition in aquatic ecosystems, its magnitude and spatiotemporal variations in aquaculture ponds remain poorly understood. In this study, we determined the rates and spatiotemporal variations of ebullitive CH4 emissions from three mariculture ponds during the aquaculture period of two years at a subtropical estuary in southeast China. Our results showed that the mean ebullitive CH4 flux from the studied ponds was 14.9 mg CH4 m−2 h−1 during the aquaculture period and accounted for over 90% of the total CH4 emission, indicating the importance of ebullition as a major CH4 transport mechanism. Ebullitive CH4 emission demonstrated a clear seasonal pattern, with a peak value during the middle stage of aquaculture. Sediment temperature was found to be an important factor influencing the seasonal variations in CH4 ebullition. Ebullitive CH4 fluxes also exhibited considerable spatial variations within the ponds, with 49.7–71.8% of the whole pond CH4 ebullition being detected in the feeding zone where the large loading of sediment organic matter fueled CH4 production. Aquaculture ponds have much higher ebullitive CH4 effluxes than other aquatic ecosystems, which indicated the urgency to mitigate CH4 emission from aquaculture activities. Our findings highlighted that the importance of considering the large spatiotemporal variations in ebullitive CH4 flux in improving the accuracy of large-scale estimation of CH4 fluxes in aquatic ecosystems. Future studies should be conducted to characterize CH4 ebullitive fluxes over a greater number and diversity of aquaculture ponds and examine the mechanisms controlling CH4 ebullition in aquatic ecosystems

Electron transfer kinetics across a dodecanethiol monolayer self assembled on gold

10.1016/S0022-0728(02)01440-7Journal of Electroanalytical Chemistry5427-11JECH

Appearance and disappearance of edge states in topological insulators

We investigate the relationship between spin Chern numbers and edge state properties in general situations, where the time-reversal symmetry may be broken. As an example, we consider a thin film of three-dimensional topological insulators sandwiched between two ferromagnetic insulators with an antiparallel magnetization configuration. A topological quantum spin Hall phase with quantized spin Chern numbers C± =  ±1, and a trivial insulator with C± = 0 are found in different parameter regions. With tuning parameters, the quantum phase transition between the two phases can occur through closing of the spin spectrum gap rather than energy gap. It is further shown that for a junction between samples with different parameters, appearance of edge states at the interface is always related to the mismatch of spin Chern numbers, independent of symmetries