A Dark Matter Hurricane: Measuring the S1 Stream with Dark Matter Detectors (1807.09004v2)

Abstract: The recently discovered S1 stream passes through the Solar neighbourhood on a low inclination, counter-rotating orbit. The progenitor of S1 is a dwarf galaxy with a total mass comparable to the present-day Fornax dwarf spheroidal, so the stream is expected to have a significant DM component. We compute the effects of the S1 stream on WIMP and axion detectors as a function of the density of its unmeasured dark component. In WIMP detectors the S1 stream supplies more high energy nuclear recoils so will marginally improve DM detection prospects. We find that even if S1 comprises less than 10% of the local density, multi-ton xenon WIMP detectors can distinguish the S1 stream from the bulk halo in the relatively narrow mass range between 5 and 25 GeV. In directional WIMP detectors such as CYGNUS, S1 increases DM detection prospects more substantially since it enhances the anisotropy of the WIMP signal. Finally, we show that axion haloscopes possess by far the greatest potential sensitivity to the S1 stream. Once the axion mass has been discovered, the distinctive velocity distribution of S1 can easily be extracted from the axion power spectrum.

• The paper establishes that the S1 stream, a counter-rotating stellar structure from a disrupted dwarf galaxy, significantly boosts dark matter detection signals.
• It demonstrates that multi-ton xenon detectors can exploit S1's high-speed particle influx to improve sensitivity for WIMPs in the 5–25 GeV mass range.
• The study highlights that directional detectors and axion haloscopes can leverage S1’s unique spectral features to achieve clearer dark matter identification.

Overview of "A Dark Matter Hurricane: Measuring the S1 Stream with Dark Matter Detectors"

The paper "A Dark Matter Hurricane: Measuring the S1 Stream with Dark Matter Detectors" by O'Hare et al. investigates the characteristics and detection potential of the S1 stream, a recently identified dark matter (DM) structure in our galaxy. This research emphasizes the interaction of the S1 stream with dark matter detectors and explores the implications for both weakly interacting massive particles (WIMPs) and axions, two leading DM candidates.

The Discovery and Nature of the S1 Stream

The S1 stream is a stellar stream thought to result from the tidal disruption of a dwarf galaxy by the Milky Way's gravitational field. This stream is counter-rotating, passes near the solar neighborhood, and thus directly contributes to the local dark matter density. The progenitor dwarf galaxy is estimated to have had a mass similar to the present-day Fornax dwarf spheroidal, likely accounting for a substantial DM component.

Detection Prospects in WIMP Detectors

For WIMP detection, the S1 stream holds promise in enhancing the detection prospects of existing and future dark matter experiments. The stream's distinct kinematic signal offers an additional high-speed influx of DM particles, which is particularly useful in exploiting energy thresholds in detectors. For instance, multi-ton xenon detectors could discern the S1 stream from the main DM halo component, especially for WIMPs with masses in the range of 5 to 25 GeV, even if S1 comprises only a small fraction (~10%) of the local DM density.

Enhancements in Directional Detection

The paper elaborates on how directional detection technology, notably in experiments such as CYGNUS, can capitalize on the anisotropic signal increase due to S1. Directional detectors benefit significantly from the S1 stream since the stream's trajectory results in clearer kinematic signals. Such detectors possess the potential to distinguish S1 over a wider mass range, making them powerful tools in DM discovery.

Axion Detection Potentials

Axion haloscopes exhibit the greatest sensitivity to the S1 stream due to their ability to probe the spectral characteristics of axions effectively. The stream can enhance detection capabilities by narrowing the axion power spectrum, improving the signal-to-noise ratio for detection. Additionally, once the axion mass is identified, the distinctive velocity distribution introduced by S1 can be inferred from the power spectrum, offering promising scope for axion-based DM astronomy.

Implications and Future Directions

The recognition of the S1 stream represents a valuable opportunity for advancing our understanding of DM substructures. Its presence can influence current detection strategies and necessitates consideration in phenomenological studies of DM. Future developments should focus on accurately quantifying the DM attributed to S1 and integrating this knowledge into the design and calibration of both WIMP and axion detection experiments.

This paper makes substantial contributions to our understanding of how regional substructures like the S1 stream can alter the landscape of DM research. Exploring the effects of such streams demonstrably underscores the need for robust and adaptive detection methodologies as we advance in the quest to identify and characterize DM components spanning both particle-like and wave-like natures.