2,313 research outputs found

    Minimally Allowed Neutrinoless Double Beta Decay Rates From Approximate Flavor Symmetries

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    Neutrinoless double beta decay (ββ0ν\beta\beta0\nu) is among the only realistic probes of Majorana neutrinos. In the standard scenario, dominated by light neutrino exchange, the process amplitude is proportional to meem_{ee}, the eee-e element of the Majorana mass matrix. Naively, current data allows for vanishing meem_{ee}, but this should be protected by an appropriate flavor symmetry. All such symmetries lead to mass matrices inconsistent with oscillation phenomenology. I perform a spurion analysis to break all possible Abelian symmetries that guarantee vanishing ββ0ν\beta\beta0\nu rates and search for minimally allowed values. I survey 230 broken structures to yield meem_{ee} values and current phenomenological constraints under a variety of scenarios. This analysis also extracts predictions for both neutrino oscillation parameters and kinematic quantities. Assuming reasonable tuning levels, I find that mee>4×106m_{ee}>4\times 10^{-6} eV at 99% confidence. Bounds below this value might indicate the Dirac neutrino nature or the existence of new light (eV-MeV scale) degrees of freedom that can potentially be probed elsewhere.Comment: 19 Pages, 4 .eps Figures, 3 Table

    Minimally Allowed Neutrinoless Double Beta Decay Rates Within an Anarchical Framework

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    Neutrinoless double beta decay is the only realistic probe of the Majorana nature of the neutrino. In the standard picture, its rate is proportional to meem_{ee}, the e-e element of the Majorana neutrino mass matrix in the flavor basis. I explore minimally allowed meem_{ee} values within the framework of mass matrix anarchy where neutrino parameters are defined statistically at low energies. Distributions of mixing angles are well defined by the Haar integration measure, but masses are dependent on arbitrary weighting functions and boundary conditions. I survey the integration measure parameter space and find that for sufficiently convergent weightings, meem_{ee} is constrained between (0.01-0.4) eV at 90% confidence. Constraints from neutrino mixing data lower these bounds. Singular integration measures allow for arbitrarily small meem_{ee} values with the remaining elements ill-defined, but this condition constrains the flavor structure of the model's ultraviolet completion. Bounds below mee5×103m_{ee} \sim 5\times10^{-3} eV should indicate symmetry in the lepton sector, new light degrees of freedom or the Dirac nature of the neutrino.Comment: BibTeX, 7 pages, 1 .eps Figure, Modified to match content of published paper: References added, table added, clarified discussion. Results are unchange

    Factors Influencing Selection of Information Sources by Cotton Producers Considering Adoption of Precision Agriculture Technologies

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    Acknowledgements: The authors thank Cotton Incorporated and the Tennessee Agricultural Experiment Station for financial supportInformation source use decisions, Precision Agriculture Technologies, Extension, Media, Private sources, Multivariate Probit, Teaching/Communication/Extension/Profession, Q12, Q16,

    Factors Influencing the Selection of Precision Farming Information Sources by Cotton Producers

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    Precision farming information demanded by cotton producers is provided by various suppliers, including consultants, farm input dealerships, University Extension systems, and media sources. Factors associated with the decisions to select among information sources to search for precision farming information are analyzed using a multivariate probit regression accounting for correlation among the different selection decisions. Factors influencing these decisions are age, education, and income. These findings should be valuable to precision farming information providers who may be able to better meet their target clientele needs.Extension, information-source-use decisions, media, multivariate probit, precision agriculture technologies, private sources, Farm Management, Teaching/Communication/Extension/Profession,

    Economics of Field Pea Supplementation for Cattle Grazing Crested Wheatgrass

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    Heifers grazing crested wheat grass were supplemented either field peas or dried distillers grains plus solubles (DDGS) at 0.4% or 0.8% of body weight. Heifers supplemented with field peas had 10% lower daily gain compared to their DDGS supplemented counterparts. The decision to supplement field peas for producers depends on the price at which field peas can be acquired, as well as the distance that DDGS has to be hauled in order to be utilized. Field peas are a viable option in western Nebraska as a supplement for grazing cattle when DDGS is unavailable or field peas are in excess and can be obtained below the human consumption and pet food market price

    The test case of HD26965: difficulties disentangling weak Doppler signals from stellar activity

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    We report the discovery of a radial velocity signal that can be interpreted as a planetary-mass candidate orbiting the K dwarf HD26965, with an orbital period of 42.364±\pm0.015 days, or alternatively, as the presence of residual, uncorrected rotational activity in the data. Observations include data from HIRES, PFS, CHIRON, and HARPS, where 1,111 measurements were made over 16 years. Our best solution for HD26965 bb is consistent with a super-Earth that has a minimum mass of 6.92±\pm0.79 M_{\oplus} orbiting at a distance of 0.215±\pm0.008 AU from its host star. We have analyzed the correlation between spectral activity indicators and the radial velocities from each instrument, showing moderate correlations that we include in our model. From this analysis, we recover a \sim38 day signal, which matches some literature values of the stellar rotation period. However, from independent Mt. Wilson HK data for this star, we find evidence for a significant 42 day signal after subtraction of longer period magnetic cycles, casting doubt on the planetary hypothesis for this period. Although our statistical model strongly suggests that the 42-day signal is Doppler in origin, we conclude that the residual effects of stellar rotation are difficult to fully model and remove from this dataset, highlighting the difficulties to disentangle small planetary signals and photospheric noise, particularly when the orbital periods are close to the rotation period of the star. This study serves as an excellent test case for future works that aim to detect small planets orbiting `Sun-like' stars using radial velocity measurements.Comment: 16 pages, 10 figures, 13 tables, accepted for publication in A

    Inherent Rheology of a Granular Fluid in Uniform Shear Flow

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    In contrast to normal fluids, a granular fluid under shear supports a steady state with uniform temperature and density since the collisional cooling can compensate locally for viscous heating. It is shown that the hydrodynamic description of this steady state is inherently non-Newtonian. As a consequence, the Newtonian shear viscosity cannot be determined from experiments or simulation of uniform shear flow. For a given degree of inelasticity, the complete nonlinear dependence of the shear viscosity on the shear rate requires the analysis of the unsteady hydrodynamic behavior. The relationship to the Chapman-Enskog method to derive hydrodynamics is clarified using an approximate Grad's solution of the Boltzmann kinetic equationComment: 10 pages, 4 figures; substantially enlarged version; to be published in PR

    Long-lived space observatories for astronomy and astrophysics

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    NASA's plan to build and launch a fleet of long-lived space observatories that include the Hubble Space Telescope (HST), the Gamma Ray Observatory (GRO), the Advanced X Ray Astrophysics Observatory (AXAF), and the Space Infrared Telescope Facility (SIRTF) are discussed. These facilities are expected to have a profound impact on the sciences of astronomy and astrophysics. The long-lived observatories will provide new insights about astronomical and astrophysical problems that range from the presence of planets orbiting nearby stars to the large-scale distribution and evolution of matter in the universe. An important concern to NASA and the scientific community is the operation and maintenance cost of the four observatories described above. The HST cost about 1.3billion(1984dollars)tobuildandisestimatedtorequire1.3 billion (1984 dollars) to build and is estimated to require 160 million (1986 dollars) a year to operate and maintain. If HST is operated for 20 years, the accumulated costs will be considerably more than those required for its construction. Therefore, it is essential to plan carefully for observatory operations and maintenance before a long-lived facility is constructed. The primary goal of this report is to help NASA develop guidelines for the operations and management of these future observatories so as to achieve the best possible scientific results for the resources available. Eight recommendations are given
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