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Dark Matter
Dark Matter

The direct detection of dark matter is one of the biggest contemporary challenges in experimental physical. Evidence that the matter in the Universe is dominated by an invisible component has been accumulating for many years, initially from measurements of the rotation curves of spiral galaxies, and the speeds of individual galaxies within clusters; and more recently from precision measurements of the cosmic microwave background. Astrophysical evidence, together with precision cosmology results suggest that in a ΛCDM model there are contributions from dark energy (68%), baryonic matter (5%) and dark matter (27%).

Particle physics theories provide a possible explanation for dark matter in the form of WIMPs - weakly interacting massive particles. WIMP candidates include the neutralino, a possible lightest supersymmetric particle; and  Kaluza Klein particles associated with compactified extra dimensions. Particle accelerator experiments such as those at the LHC aim to produce these particles; however the only way to conclusively show that they account for dark matter in the galaxy, would be by the confirmed discovery of direct WIMP interactions. This is the aim of direct dark matter search experiments, such as LUX-ZEPLIN

The scattering cross section of a supersymmetric WIMP off atomic nuclei is expected to be very low, around or below 10-10pb, corresponding to only a few events a year in a one tonne detector. Detecting such rare events requires very sensitive detectors with excellent background discrimination.

Image of the Bullet Cluster (1E 0657-56). The distribution of dark matter (shown in blue) can be inferred from gravitational lensing. This is separated from the distribution of hot gas (shown in red), supporting the dark matter hypothesis. Photo NASA.



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