Dark Matter vs. Neutrinos: The effect of astrophysical uncertainties and timing information on the neutrino floor

Future multi-tonne Direct Detection experiments will be sensitive to solar neutrino induced nuclear recoils which form an irreducible background to light Dark Matter searches. Indeed for masses around 6 GeV the spectra of neutrinos and Dark Matter are so similar that experiments will run into a neutrino floor, for which sensitivity increases only marginally with exposure past a certain cross section. In this work we show that this floor can be overcome using the different annual modulation expected from solar neutrinos and Dark Matter. Specifically for cross sections below the neutrino floor the DM signal is observable through a phase shift and a smaller amplitude for the time-dependent event rate. This allows the exclusion power to be improved by up to an order of magnitude for large exposures. In addition we demonstrate that the neutrino floor exists over a wider mass range than has been previously shown, since the large uncertainties in the Dark Matter velocity distribution make the signal spectrum harder to distinguish from the neutrino background. However for most velocity distributions the neutrino floor can still be surpassed using timing information, though certain velocity streams may prove problematic.Comment: 18 pages, 7 figures. v2: Matches version published in JCAP. Includes clarifications to the text and a new figur

Fitting the annual modulation in DAMA with neutrons from muons and neutrinos

The DAMA/LIBRA experiment searches for evidence of Dark Matter scattering off nuclei. Data from DAMA show 9.2 sigma evidence for an annual modulation, consistent with Dark Matter having a cross section around 2x10^(-40) cm^2. However this is excluded by other Direct Detection experiments. We propose an alternative source of annual modulation in the form of neutrons, which have been liberated from material surrounding the detector by a combination of 8B solar neutrinos and atmospheric muons. The phase of the muon modulation lags 30 days behind the data, however we show that adding the modulated neutrino component shifts the phase of the combined signal forward. In addition we estimate that neutrinos and muons need around 1000 m^3 of scattering material in order to generate enough neutrons to constitute the signal. With current data our model gives as good a fit as Dark Matter and we discuss prospects for future experiments to discriminate between the two.Comment: v2: Matches version published in PRL. Includes a new figure. 5 pages, 4 figure

Projections for measuring the size of the solar core with neutrino-electron scattering

We quantify the amount of data needed in order to measure the size and position of the $^8$B neutrino production region within the solar core, for experiments looking at elastic scattering between electrons and solar neutrinos. The directions of the electrons immediately after scattering are strongly correlated with the incident directions of the neutrinos, however this is degraded significantly by the subsequent scattering of these electrons in the detector medium. We generate distributions of such electrons for different neutrino production profiles, and use a maximum likelihood analysis to make projections for future experimental sensitivity. We find that with approximately 20 years worth of data the Super Kamiokande experiment could constrain the central radius of the shell in which $^8$B neutrinos are produced to be less than 0.22 of the total solar radius at 95% confidence.Comment: 5 pages, 2 figures. Matches version accepted to PRL. Improved 2D analysis and results discussio

The Past and Future of Light Dark Matter Direct Detection

We review the status and future of direct searches for light dark matter. We start by answering the question: `Whatever happened to the light dark matter anomalies?' i.e. the fate of the potential dark matter signals observed by the CoGeNT, CRESST-II, CDMS-Si and DAMA/LIBRA experiments. We discuss how the excess events in the first two of these experiments have been explained by previously underestimated backgrounds. For DAMA we summarise the progress and future of mundane explanations for the annual modulation reported in its event rate. Concerning the future of direct detection we focus on the irreducible background from solar neutrinos. We explain broadly how it will affect future searches and summarise efforts to mitigate its effects.Comment: Invited review article for the International Journal of Modern Physics A. 20 pages, 3 figure

Probing sub-GeV mass SIMP dark matter with a low-threshold surface experiment

Using data from the $\nu$-cleus detector, based on the surface of the Earth, we place constraints on dark matter in the form of Strongly Interacting Massive Particles (SIMPs) which interact with nucleons via nuclear-scale cross sections. For large SIMP-nucleon cross sections the sensitivity of traditional direct dark matter searches using underground experiments is limited by the energy loss experienced by SIMPs, due to scattering with the rock overburden and experimental shielding on their way to the detector apparatus. Hence a surface-based experiment is ideal for a SIMP search, despite the much larger background, resulting from the lack of shielding. We show using data from a recent surface run of a low-threshold cryogenic detector that values of the SIMP-nucleon cross section up to approximately $10^{-27}$ cm$^2$ can be excluded for SIMPs with masses above 100 MeV.Comment: 6 pages, 2 figures. v3: Matches version accepted to PR

Suspension Testing of 3 Heavy Vehicles - Methodology and Preliminary Frequency Analysis

Three air-sprung heavy vehicles (HVs) were instrumented and tested on typical suburban and highway road sections at typical operational speeds. The vehicles used were a tri-axle semi-trailer towed with a prime mover, an interstate coach with 3 axles and a school bus with 2 axles. The air springs (air bags) of the axle/axle group of interest were configured such that they could be connected using either standard longitudinal air lines or an innovative suspension system comprising larger-than-standard longitudinal air lines. Data for dynamic forces on axles, wheels and chassis were gathered for the purposes of: analysis of the relative performance of the HVs for the two sizes of air lines; informing the QUT/Main Roads project Heavy vehicle suspensions – testing and analysis; and providing a reference source for future projects. This reports sets down the methodology and preliminary results of the testing carried out. Accordingly, Fast-Fourier plots are provided to show indicative frequency spectra for HV axles, wheel forces and air springs during typical use. The results are documented in Appendices 3 to 5. There appears to be little or no correlation between dynamic forces in the air springs and the wheel forces in the HVs tested. Axle-hop at frequencies between 10-15 Hz predominated for unsprung masses in the HV suspensions tested. Air-spring forces are present in the sub-1.0 Hz to approximately 2 Hz frequency range. With the qualification that only one set of data from each test speed is presented herein, in general, the peaks in the frequency spectra of the body-bounce forces and wheel forces were reduced for the tests with the larger longitudinal air lines. More research needs to be done on the load sharing mechanisms between axles on air-sprung HVs. In particular, how and whether improved load sharing can be effected and whether better load sharing between axles will reduce dynamic wheel and chassis forces. This last point, in particular, in relation to the varied dynamic measures used by the HV testing community to compare different suspension types

Glow in the Dark Matter: Observing galactic halos with scattered light

We consider the observation of diffuse halos of light around the discs of spiral galaxies, as a probe of the interaction cross section between Dark Matter and photons. Using the galaxy M101 as an example, we show that for a scattering cross section at the level of 10^(-23) x (m/GeV) cm^2 or greater Dark Matter in the halo will scatter light out from the more luminous centre of the disc to larger radii, contributing to an effective increased surface brightness at the edges of the observed area on the sky. This allows us to set an upper limit on the DM-photon cross section using data from the Dragonfly instrument. We then show how to improve this constraint, and the potential for discovery, by combining the radial profile of DM-photon scattering with measurements at multiple wavelengths. Observation of diffuse light presents a new and potentially powerful way to probe the interactions of Dark Matter with photons, which is complimentary to existing searches.Comment: 6 pages, 3 figures: v2 matches version accepted to PRL, with an extended discussion of potential background