120566938
Direct detection of hot dark matter in the form of active and sterile neutrinos
Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM) in the Universe. We consider the beta-decaying (e.g., 3H) and EC-decaying (e.g., 163Ho) nuclei as the most promising targets to capture hot DM in the laboratory. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta decay or electron capture (EC) decay backgrounds in the (3+Ns) flavor mixing scheme. We stress that such direct measurements of hot DM might not be hopeless in the long term.
118641290
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)H -> (3)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. (C) 2010 Elsevier B.V. All rights reserved.
117727003
Neutrinos as Hot or Warm Dark Matter
Both active and sterile sub-eV neutrinos can serve for hot dark matter (DM). On the other hand, keV sterile neutrinos could be a good candidate for warm DM. The beta-decaying (e.g., H-3 and Ru-106) and EC-decaying (e.g., Ho-163) nuclei are considered as the most promising targets to capture those extremely low energy neutrinos and antineutrinos, respectively. We calculate the capture rates of relic electron neutrinos and antineutrinos against the corresponding beta-decay or EC-decay backgrounds in different flavor mixing schemes. We stress that such direct laboratory measurements of hot or warm DM might not be hopeless in the long term.
122049951
MCMC SAMPLING IN THE GLOBAL ANALYSIS OF SOLAR AND REACTOR NEUTRINO DATA
We present a global analysis of latest solar and reactor neutrino data in the three-neutrino mixing scheme by using both the simple grid scanning and the Markov Chain Monte Carlo (MCMC) sampling methods. Accuracy and efficiency of the two sampling methods are compared and advantages of the latter are discussed. The fitting results of three oscillation parameters theta(12), theta(13) and Delta m(21)(2) are provided with both old and new evaluations of the reactor antineutrino flux. Possible correlation between the fitting parameters is also discussed.
118606894
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 key 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) + H-3 -> He-3 + e(-) and nu(e) + Ru-106 -> Rh-106 + e(-) against the beta-decay backgrounds, and conclude that this experimental approach might not be hopeless in the long run. (C) 2010 Elsevier B.V. All rights reserved.
118445342
Shifts of neutrino oscillation parameters in reactor antineutrino experiments with non-standard interactions
We discuss reactor antineutrino oscillations with non-standard interactions (NSIs) at the neutrino production and detection processes. The neutrino oscillation probability is calculated with a parametrization of the NSI parameters by splitting them into the averages and differences of the production and detection processes respectively. The average parts induce constant shifts of the neutrino mixing angles from their true values, and the difference parts can generate the energy (and baseline) dependent corrections to the initial mass-squared differences. We stress that only the shifts of mass-squared differences are measurable in reactor antineutrino experiments. Taking hangmen Underground Neutrino Observatory (JUNO) as an example, we analyze how NSIs influence the standard neutrino measurements and to what extent we can constrain the NSI parameters. (C) 2014 The Authors. Published by Elsevier B.V.
124704287
Branching Fractions and Direct $CP$ Asymmetries of $\overline B_s ^0 \to K^0 h^+h^{\prime -}(h^{(\prime)}=K,\pi)$ Decays
Motivated by the recent LHCb measurements of charmless three-body decays of $B_s^0$ meson, we calculate the branching fractions of $\overline B_s ^0 \to K^0 \pi^+\pi^-$, $\overline B_s ^0 \to K^0 K^+K^-$, $\overline B_s ^0 \to K^0 \pi^+K^-$ and $\overline B_s ^0 \to \overline K^0 K^+\pi^-$ decay modes within the factorization approach. The resonant and nonresonant contributions are studied in detail. For the decays $\overline B_s ^0 \to K^0 \pi^+\pi^-$ and $\overline B_s ^0 \to K^0 K^+K^-$, our results agree well with experimental data, and the former is dominated by the $K^*$ and $K_0^*(1430)$ poles, while the later one is dominated by the nonresonant contribution. Considering the flavor $SU(3)$ symmetry violation, the sum of branching fractions of $\overline B_s ^0 \to K^0 \pi^+K^-$ and $\overline B_s ^0 \to \overline K^0 K^+\pi^-$ could accommodate the data well. It should be noted that the branching fractions are very sensitive to the scalar density $\langle K\pi| \bar s q|0\rangle$. Furthermore, the resonant contributions are dominated by the scalar poles $K_0^*(1430)$. We hope that these branching fractions could be measured separately in the experiments so as to test the factorization approach. Moreover, the direct $CP$ asymmetries of these decays are also explored, which could be measured in the running LHCb experiment and Super-b factory in future.
9377747
Stability Conditions For Topological D-branes: A Worldsheet Approach
We study conditions on the topological D-branes of types A and B obtained by requiring a proper matching of the spectral flow operators on the boundary. These conditions ensure space-time supersymmetry and stability of D-branes. In most cases, we reproduce the results of Marino-Minasian-Moore-Strominger, who studied the same problem using the supersymmetric Born-Infeld action. In some other cases, corresponding to coisotropic A-branes, our stability condition is new. Our results enable us to define an analogue of the Maslov class and grading for coisotropic A-branes. We expect that they play a role in a conjectural generalization of the Floer homology.
15144949
The abundance of voids and the excursion set formalism
We present measurements of the number density of voids in the dark matter distribu- tion from a series of N-body simulations of aCDM cosmology. We define voids as spherical regions of ρv = 0.2ρm around density minima in order to relate our results to the predicted abundances using the excursion set formalism. Using a linear underden- sity of δv = 2.7, from a spherical evolution model, we find that a volume conserving model, which does not conserve number density in the mapping from the linear to nonlinear regime, matches the measured abundance to within 16% for a range of void radii 1 10h 1 Mpc, voids compared to the dark matter. These results indicate that voids identified in the halo or galaxy distribution are related to the underlying void distribution in the dark matter in a complicated way which merits further study if voids are to be used as a precision probe of cosmology.
123193403
The rate of the sphaleron transition in the (1 + 1)-dimensional Abelian Higgs model on a circle
Abstract The rate of fermion number non-conservation at finite temperatures is discussed in the (1 + 1)-dimensional Abelian Higgs model on a circle. An effective potential is used to estimate the one-loop correction to the effective action remaining after the treatment of zero modes. With this method it is not necessary to know all the normal modes of the sphaleron. The expression of the rate is given for the case of M W ⪡ M H .
124761141
Population transfer to supercritical bound states during pair creation
We study the electron-positron pair-creation process from the vacuum under a very strong electric field. The external field is so strong that discrete states can dive into the negative energy continuum (the Dirac sea). This process is simultaneously associated with the onset of pair creation as well as the possibility for capturing the created electrons. By varying the total spatial width of the potential well, we can shift these trapping states in and out of the negative energy continuum while keeping the associated electric force the same. We compute the population transfer in and out of these states by solving the corresponding quantum field theoretical equations for the field operator on a space-time grid. We compare the population of these states obtained by projecting the time-evolved states on instantaneous energy eigenstates with the kinetic-energy spectrum of the ejected positrons.