Widening the search for Dark Matter and Physics beyond the Standard Model with direct detection experiments

Everything we can see in the Universe is only a small fraction of its mass. Most of it, an incredible 85%, is 'dark' - and we know remarkably little about it. We can infer the role of this mysterious 'Dark Matter' in the early Universe when it allowed galaxies to form and we can observe its gravitational effects today as it holds the galaxies, including our own, together.

Yet we cannot see it directly and have yet to make any detection that helps us understand its nature. Put simply, we know Dark Matter is there, but we do not know what it is! What we do know is that the Standard Model of particle physics that explains so accurately most of what we do observe cannot help us - it provides no candidates that fit the bill.

The detection of Dark Matter will not only tell us what much of our Universe is made of, it will also open the door to physics beyond the Standard Model, bringing down the veil between us and a deeper understanding of the Universe and our place within it. The effort to detect Dark Matter is worldwide - it is truly one of the most important scientific missions of our time.

Piecing together all the evidence, our best theories tell us Dark Matter is made up of tiny particles that that pervade the Universe but rarely interact - millions of Dark Matter particles are passing harmlessly through you as you read this right now. Just occasionally one of them may bounce off the nucleus of an atom, giving it a tiny kick of energy.

Observing such a 'direct' scatter is the only way to be sure that we have seen Dark Matter from our own galaxy; born in the Big Bang and present ever since. But to have any hope of seeing such tiny, rare signals requires experiments like no other: large detectors, sensitive to the recoil of a single atom, constructed from the most radio-pure materials and buried deep under the surface of the Earth.

LUX-ZEPLIN (LZ) will be the largest and most advanced experiment ever built in the direct search for Dark Matter. LZ will come online in 2019 and operate for 3-years in a former gold mine turned science laboratory 1.5 km underground in S. Dakota, USA.

I am a leading researcher in the LZ experiment, responsible for the simulations that helped us to design it; that model the level of 'background' from Standard Model processes that may mask Dark Matter signatures; and that establish the experiment's science reach. LZ will be over 10 times more sensitive than earlier experiments and its unprecedented scale and ultra-low background environment will herald a new era in direct searches.

In addition to exploring the bulk of the remaining uncharted territory in search of Weakly Interacting Massive Particles (WIMPs), the most popular candidate for dark matter, LZ will now have sensitivity and discovery potential to a whole host of equally well-motivated alternative (non-WIMP) Dark Matter candidates and other physics beyond the Standard Model. Key to these searches is my expertise in modelling background processes, in exploiting multiple signal channels across the full energy range available to LZ, and in developing software to recognise complex signals from wholly unexpected physics.

I will take leading roles in the WIMP and alternative model searches from LZ to uncover groundbreaking discoveries.

Alongside physics analyses and software, I have developed new hardware capability in the UK with world-class mass-spectrometry to measure trace radioactivity in materials. This technique is crucial to building any future experiment needed to confirm discovery, perform high-precision measurements of signal, or explore the last of the available parameter space available for WIMPs.

Such an experiment would have incredible sensitivity to the alternative models and beyond Standard Model physics, such as neutrino-less double beta decay. My mass-spectrometry research will meet the stringent radio-purity needs for future generation experiments and feed the background model upon which all the science rests.