Alladi Ramakrishnan Hall

The Reverse Rutherford Era​ of Dark Matter

Dr. Nirmal Raj

TRIUMF, Canada

Dark matter -- the invisible substance that makes up four-fifths of all matter -- is ubiquitous, yet efforts to identify its microscopic nature have proven elusive. As it is known to move at high speeds, a promising approach to detect it is to observe unusual effects of its scattering on well-understood stationary targets, essentially the Rutherford scattering experiment in reverse. I will outline two experiments that I have proposed:

(1) Through scattering, dark matter could set ancient neutron stars on fire, which may be observed by infrared telescopes such as the recently launched James Webb, and the imminent Thirty Meter Telescope and Extremely Large Telescope, and under special conditions by optical and ultraviolet missions. Observing the kinetic heating of neutron stars would be the most extensive method to date for detecting dark matter.

(2) One reason for why dedicated detectors on Earth looking for dark matter particles have found none so far could be that these particles are very dilute, at least kilometres apart. I will discuss new strategies to catch them at metre-scale detectors such as XENON and PICO, and by repurposing larger neutrino detectors such as BOREXINO, SNO+, and JUNO. I will describe a search I performed in collaboration with the DEAP-3600 experiment (2108.09405), placing the first laboratory limits on particle dark matter at the Planck scale (~ 10^19 GeV).