Nuclear Shell Model Calculations of Neutralino-Nucleus Cross Sections for Silicon 29 and Germanium 73

We present the results of detailed nuclear shell model calculations of the spin-dependent elastic cross section for neutralinos scattering from \si29 and \ge73. The calculations were performed in large model spaces which adequately describe the configuration mixing in these two nuclei. As tests of the computed nuclear wave functions, we have calculated several nuclear observables and compared them with the measured values and found good agreement. In the limit of zero momentum transfer, we find scattering matrix elements in agreement with previous estimates for \si29 but significantly different than previous work for \ge73. A modest quenching, in accord with shell model studies of other heavy nuclei, has been included to bring agreement between the measured and calculated values of the magnetic moment for \ge73. Even with this quenching, the calculated scattering rate is roughly a factor of 2 higher than the best previous estimates; without quenching, the rate is a factor of 4 higher. This implies a higher sensitivity for germanium dark matter detectors. We also investigate the role of finite momentum transfer upon the scattering response for both nuclei and find that this can significantly change the expected rates. We close with a brief discussion of the effects of some of the non-nuclear uncertainties upon the matrix elements.Comment: 31 pages, figures avaiable on request, UCRL-JC-11408

Large Extra Dimension Effects on the Spin Configuration of the Top Quark Pair at e^+ e^- Colliders

Large extra dimension effects on the spin configuration of the top quark pair at the $e^+ e^-\to t\bar{t}$ process are studied. It is shown that the TeV scale quantum gravity effects cause significant deviations from the Standard Model predictions for the spin configuration in the off-diagonal basis: they lead to substantial cross sections of the like-spin states of the top quark pair, which vanish in the SM; they weaken the pure dominance of the processes, the Up-Down (Down-Up) spin states for the left-handed (right-handed) beam. In addition it is shown that the angular cut $-0.5<\cos\theta<0$ is very effective to determine the sign of the quantum gravity corrections.Comment: A discussion on the angular distribution is added with a tabl

Zoonosis emergence linked to agricultural intensification and environmental change

A systematic review was conducted by a multidisciplinary team to analyze qualitatively best available scientific evidence on the effect of agricultural intensification and environmental changes on the risk of zoonoses for which there are epidemiological interactions between wildlife and livestock. The study found several examples in which agricultural intensification and/or environmental change were associated with an increased risk of zoonotic disease emergence, driven by the impact of an expanding human population and changing human behavior on the environment. We conclude that the rate of future zoonotic disease emergence or reemergence will be closely linked to the evolution of the agriculture–environment nexus. However, available research inadequately addresses the complexity and interrelatedness of environmental, biological, economic, and social dimensions of zoonotic pathogen emergence, which significantly limits our ability to predict, prevent, and respond to zoonotic disease emergence

Broad Line Region Physical Conditions along the Quasar Eigenvector 1 Sequence

[Abridged] We compare broad emission line profiles and estimate line ratios for all major emission lines between Ly-alpha and H-beta in a sample of six quasars. The sources were chosen with two criteria in mind: the existence of high quality optical and UV spectra as well as the possibility to sample the spectroscopic diversity in the 4D Eigenvector 1 context . In the latter sense each source occupies a region (bin) in the FWHM(H-beta) vs. optical FeII strength plane that is significantly different from the others. High S/N H-beta emission line profiles are used as templates for modeling the other lines (Ly-alpha, CIV 1549, HeII 1640, Al III 1860, Si III] 1892, and Mg II 2800). We can adequately model all broad lines assuming the existence of three components distinguished by blueshifted, unshifted and redshifted centroids (indicated as blue, broad and very broad component respectively). The broad component (high electron density, low ionization parameter; high column density) is present in almost all type-1 quasars and therefore corresponds most closely to the classical broad line emitting region (the reverberating component). The blue component emission (lower electron density; high ionization; low column density) arises in less optically thick gas; it is often thought to arise in an accretion disk wind. The least understood component involves the very broad component (high ionization and large column density). It is perhaps the most distinguishing characteristic of quasars with FWHM H-beta > 4000 km/s that belong to the so-called Population B of our 4DE1 space. Population A quasars (FWHM H-beta < 4000 km/s) are dominated by broad component emission in H-beta and blue component emission in CIV 1549 and other high ionization lines. 4DE1 appears to be the most useful current context for revealing and unifying spectral diversity in type-1 quasars.Comment: 7 Tables, 5 Figures; accepted for publication in Monthly Notices of the Royal Astronomical Societ

Weak reaction freeze-out constraints on primordial magnetic fields

We explore constraints on the strength of the primordial magnetic field based upon the weak reaction freeze-out in the early universe. We find that limits on the strength of the magnetic field found in other works are recovered simply by examining the temperature at which the rate of weak reactions drops below the rate of universal expansion ($\Gamma_{w} \le$ H). The temperature for which the $n/p$ ratio at freeze-out leads to acceptable helium production implies limits on the magnetic field. This simplifies the application of magnetic fields to other cosmological variants of the standard big-bang. As an illustration we also consider effects of neutrino degeneracy on the allowed limits to the primordial magnetic field.Comment: Submitted to Phys. Rev. D., 6 pages, 2 figure

The Nab Experiment: A Precision Measurement of Unpolarized Neutron Beta Decay

Neutron beta decay is one of the most fundamental processes in nuclear physics and provides sensitive means to uncover the details of the weak interaction. Neutron beta decay can evaluate the ratio of axial-vector to vector coupling constants in the standard model, $\lambda = g_A / g_V$, through multiple decay correlations. The Nab experiment will carry out measurements of the electron-neutrino correlation parameter $a$ with a precision of $\delta a / a = 10^{-3}$ and the Fierz interference term $b$ to $\delta b = 3\times10^{-3}$ in unpolarized free neutron beta decay. These results, along with a more precise measurement of the neutron lifetime, aim to deliver an independent determination of the ratio $\lambda$ with a precision of $\delta \lambda / \lambda = 0.03\%$ that will allow an evaluation of $V_{ud}$ and sensitively test CKM unitarity, independent of nuclear models. Nab utilizes a novel, long asymmetric spectrometer that guides the decay electron and proton to two large area silicon detectors in order to precisely determine the electron energy and an estimation of the proton momentum from the proton time of flight. The Nab spectrometer is being commissioned at the Fundamental Neutron Physics Beamline at the Spallation Neutron Source at Oak Ridge National Lab. We present an overview of the Nab experiment and recent updates on the spectrometer, analysis, and systematic effects.Comment: Presented at PPNS201

A high resolution VLT/FLAMES study of individual stars in the centre of the Fornax dwarf spheroidal galaxy

For the first time we show the detailed late-stage chemical evolution history of small nearby dwarf spheroidal galaxy in the Local Group. We present the results of a high resolution (R$\sim$20000) FLAMES/GIRAFFE abundance study at ESO/VLT of 81 photometrically selected red giant branch stars in the central 25$'$ of the Fornax dwarf spheroidal galaxy. We present abundances of \alfe\ (Mg, Si, Ca and Ti), iron-peak elements (Fe, Ni and Cr) and heavy elements (Y, Ba, La, Nd and Eu). Our sample was randomly selected, and is clearly dominated by the younger and more metal rich component of Fornax which represents the major fraction of stars in the central region. This means that the majority of our stars are 1$-$4 Gyr old, and thus represent the end phase of chemical evolution in this system. Our sample of stars has unusually low [$\alpha$/Fe], [Ni/Fe] and [Na/Fe] compared to the Milky Way stellar populations at the same [Fe/H]. The particularly important role of stellar winds from low metallicity AGB stars in the creation of s-process elements is clearly seen from the high [Ba/Y]. Furthermore, we present evidence for an s-process contribution to Eu.Comment: 40 pages, 20 figures, accepted for publication in A&

Galactic winds driven by cosmic-ray streaming

Galactic winds are observed in many spiral galaxies with sizes from dwarfs up to the Milky Way, and they sometimes carry a mass in excess of that of newly formed stars by up to a factor of ten. Multiple driving processes of such winds have been proposed, including thermal pressure due to supernova-heating, UV radiation pressure on dust grains, or cosmic ray (CR) pressure. We here study wind formation due to CR physics using a numerical model that accounts for CR acceleration by supernovae, CR thermalization, and advective CR transport. In addition, we introduce a novel implementation of CR streaming relative to the rest frame of the gas. We find that CR streaming drives powerful and sustained winds in galaxies with virial masses M_200 < 10^{11} Msun. In dwarf galaxies (M_200 ~ 10^9 Msun) the winds reach a mass loading factor of ~5, expel ~60 per cent of the initial baryonic mass contained inside the halo's virial radius and suppress the star formation rate by a factor of ~5. In dwarfs, the winds are spherically symmetric while in larger galaxies the outflows transition to bi-conical morphologies that are aligned with the disc's angular momentum axis. We show that damping of Alfven waves excited by streaming CRs provides a means of heating the outflows to temperatures that scale with the square of the escape speed. In larger haloes (M_200 > 10^{11} Msun), CR streaming is able to drive fountain flows that excite turbulence. For halo masses M_200 > 10^{10} Msun, we predict an observable level of H-alpha and X-ray emission from the heated halo gas. We conclude that CR-driven winds should be crucial in suppressing and regulating the first epoch of galaxy formation, expelling a large fraction of baryons, and - by extension - aid in shaping the faint end of the galaxy luminosity function. They should then also be responsible for much of the metal enrichment of the intergalactic medium.Comment: 25 pages, 14 figures, accepted by MNRA