Megaton Water Cerenkov Detectors and Astrophysical Neutrinos

Although formal proposals have not yet been made, the UNO and Hyper-Kamiokande projects are being developed to follow-up the tremendously successful program at Super-Kamiokande using a detector that is 20-50 times larger. The potential of such a detector to continue the study of astrophysical neutrinos is considered and contrasted with the program for cubic kilometer neutrino observatories.Comment: 4 pages Submitted to the Proceedings of the 2004 Neutrino Oscillation Workshop, Otranto Ital

Astrophysical Interplay in Dark Matter Searches

I discuss recent progress in dark matter searches, focusing in particular on how rigorous modeling the dark matter distribution in the Galaxy and in its satellite galaxies improves our interpretation of the limits on the annihilation and elastic scattering cross sections. Looking forward to indirect and direct searches that will operate during the next decade, I review methods for extracting the properties of the dark matter in these experiments in the presence of unknown Galactic model parameters.Comment: Contribution to proceedings of CETUP* workshop in Lead, South Dakota, July 10 - August 1, 201

The Cosmic Abundance of Classical Milky Way Satellites

We study the abundance of satellites akin to the brightest, classical dwarf spheroidals around galaxies similar in magnitude and isolation to the Milky Way and M31 in the Sloan Digital Sky Survey. From a combination of photometric and spectroscopic redshifts, we bound the mean and the intrinsic scatter in the number of satellites down to ten magnitudes fainter than the Milky Way. Restricting to magnitudes brighter than Sagittarius, we show that the Milky Way is not a significant statistical outlier in its population of classical dwarf spheroidals. At fainter magnitudes, we find an upper limit of 13 on the mean number of satellites brighter than the Fornax dwarf spheroidal. Methods to improve these limits that utilize full photometric redshift distributions hold promise, but are currently limited by incompleteness at the very lowest redshifts. Theoretical models are left to explain why the majority of dark matter subhalos that orbit Milky Way-like galaxies are inefficient at making galaxies at the luminosity scale of the brightest dwarf spheroidals, or why these subhalos predicted by Lambda-CDM do not exist.Comment: 8 pages, 2 figure

Implication of neutrino backgrounds on the reach of next generation dark matter direct detection experiments

As direct dark matter experiments continue to increase in size, they will become sensitive to neutrinos from astrophysical sources. For experiments that do not have directional sensitivity, coherent neutrino scattering (CNS) from several sources represents an important background to understand, as it can almost perfectly mimic an authentic WIMP signal. Here we explore in detail the effect of neutrino backgrounds on the discovery potential of WIMPs over the entire mass range of 500 MeV to 10 TeV. We show that, given the theoretical and measured uncertainties on the neutrino backgrounds, direct detection experiments lose sensitivity to light (~10 GeV) and heavy (~100 GeV) WIMPs with a spin-independent cross section below 10^{-45} cm^2 and 10^{-49} cm^2, respectively.Comment: 15 pages, 12 figures, 7Be fluxes revised, conclusions unchange

Kinematics of Milky Way Satellites: Mass Estimates, Rotation Limits, and Proper Motions

In the past several years high resolution kinematic data sets from Milky Way satellite galaxies have confirmed earlier indications that these systems are dark matter dominated objects. Further understanding of what these galaxies reveal about cosmology and the small scale structure of dark matter relies in large part on a more detailed interpretation of their internal kinematics. This article discusses a likelihood formalism that extracts important quantities from the kinematic data, including the amplitude of rotation, proper motion, and the mass distribution. In the simplest model the projected error on the rotational amplitude is shown to be $\sim 0.5$ km s$^{-1}$ with $\sim 10^3$ stars from either classical or ultra-faint satellites. The galaxy Sculptor is analyzed for the presence of a rotational signal; no significant detection of rotation is found, and given this result limits are derived on the Sculptor proper motion. A criteria for model selection is discussed that determines the parameters required to describe the dark matter halo density profiles and the stellar velocity anisotropy. Applied to four data sets with a wide range of velocities, the likelihood is found to be more sensitive to variations in the slope of the dark matter density profile than variations in the velocity anisotropy. Models with variable radial velocity anisotropy are shown to be preferred relative to those in which this quantity is constant at all radii in the galaxy.Comment: 20 pages. To appear in Advances in Astronomy, Dwarf-Galaxy Cosmology issu

Complementarity of dark matter detectors in light of the neutrino background

Direct detection dark matter experiments looking for WIMP-nucleus elastic scattering will soon be sensitive to an irreducible background from neutrinos which will drastically affect their discovery potential. Here we explore how the neutrino background will affect future ton-scale experiments considering both spin-dependent and spin-independent interactions. We show that combining data from experiments using different targets can improve the dark matter discovery potential due to target complementarity. We find that in the context of spin-dependent interactions, combining results from several targets can greatly enhance the subtraction of the neutrino background for WIMP masses below 10 GeV/c$^2$ and therefore probe dark matter models to lower cross-sections. In the context of target complementarity, we also explore how one can tune the relative exposures of different target materials to optimize the WIMP discovery potential.Comment: 13 pages, 12 figures, 3 table

Non-standard interactions of solar neutrinos in dark matter experiments

Non-standard neutrino interactions (NSI) affect both their propagation through matter and their detection, with bounds on NSI parameters coming from various astrophysical and terrestrial neutrino experiments. In this paper, we show that NSI can be probed in future direct dark matter detection experiments through both elastic neutrino-electron scattering and coherent neutrino-nucleus scattering, and that these channels provide complementary probes of NSI. We show NSI can increase the event rate due to solar neutrinos, with a sharp increase for lower nuclear recoil energy thresholds that are within reach for upcoming detectors. We also identify an interference range of NSI parameters for which the rate is reduced by approximately 40\%. Finally, we show that the "dark side" solution for the solar neutrino mixing angle may be discovered at forthcoming direct detection experiments.Comment: 12 pages, 5 figure