‘Tis the season

South Australia in January/February is even more laid back than usual. Christmas and New Year have gone, followed by wonderful summer holidays, then a month of festivals and frivolity. Along with the wonderful weather (perhaps a little too hot at times) and general good mood it’s a happy place. Indeed, January is the month academics are supposed to be taking their vacation, much like August in Europe. However, with the deadlines for Australia Research Council grant applications looming in February and the ATLAS collaboration rush to get results sent to journal prior to the March conference season, January tends to be busy for me. I’m also organising the national meeting of our Centre of Excellence for Particle Physics on the beach at Glenelg, SA. It’s an exciting time for our work so I’m certainly not complaining.

Everything’s turned around down here – we’re finalising results for winter conferences, in the summertime! This month my group, and our collaborators around the world, are pushing out two results searching for evidence of supersymmetric (SUSY) particles. SUSY essentially duplicates the particle spectrum, taking each of the standard model particles and either adding an ‘s’ to the front, making ‘squarks’ to partner the quarks, or appending ‘ino’ to the end of particles with ‘gluons’ becoming ‘gluinos’. So you can think of slaughter as simply supersymmetric laughter!

To search for these new particles we’re employing a technique that I co-developed (called ‘the Recursive Jigsaw Reconstruction’) to look for heavy, pair-produced particles decaying to visible objects and potentially heavy invisible objects. It’s a compelling signature to consider, SUSY or not, as it would give us new states to solve some of the issues the Standard Model presents, and maybe hints at the mass range of the invisible dark matter all particle physicists are craving the evidence for.

We’re also tackling trickier scenarios, where the decays are “compressed” - meaning the parent particle and it’s child are similar in mass, leaving little phase space to produce high-momentum objects. Along with my student and collaborator, I submitted to journal a paper describing a technique we’ve been employing in the ATLAS collaboration, and how it can be used, to good effect, in our new physics searches. Inventing a method and employing it within an experiment is thrilling. It takes work, as it should, to convince collaborators to try new things, but is incredibly gratifying and fulfilling to see your ideas being used.

I’m scribing this piece while attending a workshop in Melbourne ‘Connecting Astrophysical Dark Matter with Direct Detection’, to be followed by a one-day CYGNUS proto-collaboration meeting. The workshop is focused on the synergy between astrophysical studies and direct detection of dark matter, with a special emphasis on what future directional dark matter detectors can offer. Our aim is to build better connections between the astrophysics and experimental particle physics communities, united in the quest to identify and characterize dark matter. It’s exciting stuff! We’re building experiments in Southern Australia at the Stawell Underground Physics Laboratory, where there is a strong push to situate a first Australian dark matter experiment (named SABRE-south) in the very near future. SABRE will have partner experiments situated at Gran Sasso, Italy and Stawell to test for the putative, and controversial, signal for dark matter from the DAMA/LIBRA experiment. With an annual modulation having been observed there is the question of seasonal variation being an important thing to pin down. So, just maybe, we can use the winter vs summer ‘confusion’ to our advantage and by sharing our seasons we can hone in on the nature of dark matter - one of the biggest mysteries in particle physics.