119294844
Matter Effects in Solar Neutrino Active-Sterile Oscillations
We study the matter effects for solar neutrino oscillations in a general scheme, without any constraint on the number of sterile neutrinos and the mixing matrix elements, only assuming a realistic hierarchy of neutrino squared-mass differences in which the smallest squared-mass difference is effective in solar neutrino oscillations. The validity of the analytic results are illustrated with a numerical solution of the evolution equation in the simplest case of four-neutrino mixing with the realistic matter density profile inside the Sun.
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.
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.
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.
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.
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.
37310101
DEVELOPMENT AND MEASUREMENT OF STRAIN FREE RF PHOTOINJECTOR VACUUM WINDOWS *
RF photoinjectors produce the highest brightness electron bunches only under nearly ideal illumination by a drive laser [1]. The vacuum window used to introduce the laser beam is an essential element that may potentially degrade the distribution, making it difficult or impossible to know the actual uniformity achieved at the cathode. Because of the necessity to obtain ultrahigh vacuum near the photoinjector, some restrictions are imposed on the fabrication technology available to manufacture distortion-free windows. At the UV wavelengths commonly used for photoinjectors, it is challenging to measure and eliminate degradation caused by vacuum windows. Here, we discuss the initial measurements of a strain-free, coated, UHV window manufactured by Insulator Seal in collaboration with members of Brookhaven and Argonne National Laboratories.
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.
4995821
Drell-Yan lepton pair production at NNLO QCD with parton showers
We present a simple approach to combine NNLO QCD calculations and parton showers, based on the unlops technique. We apply the method to the computation of Drell-Yan lepton-pair production at the Large Hadron Collider. We comment on possible improvements and intrinsic uncertainties.
13345134
D-branes in topological minimal models: the Landau–Ginzburg approach
We study D-branes in topologically twisted N = 2 minimal models using the Landau-Ginzburg realization. In the cases of A and D-type minimal models we provide what we believe is an exhaustive list of topological branes and compute the corresponding boundary OPE algebras as well as all disk correlators. We also construct examples of topological branes in E-type minimal models. We compare our results with the boundary state formalism, where possible, and find agreement.
116807042
Disentangling radiative corrections using the high-mass Drell-Yan process at the LHC
We present a detailed numerical study of lepton-pair production via the Drell-Yan process above the Z-peak at the LHC. Our results consistently combine next-to-next-to-leading order QCD corrections and next-to-leading order electroweak effects, and include the leading photon-initiated processes using a recent extraction of the photon distribution function. We focus on the effects of electroweak corrections and of photon-photon scattering contributions, and demonstrate which kinematic distributions exhibit sensitivity to these corrections. We show that a combination of measurements allows them to be disentangled and separately determined.