Sue Ann Koay

Sue Ann Koay is a Dicke Fellow in the Physics department, who came to Princeton after graduating from the University of California Santa Barbara. She started graduate school on a String Theory track, but ventured into experimental physics in hopes of collecting data fundamental to the testing of such lofty descriptions of the universe.

The Large Hadron Collider (LHC) at CERN, Switzerland, is the highest energy particle collider built to date. It is designed to be a discovery machine, capable of simultaneously probing broad swaths of initial states times phase spaces for reactions not predicted by the Standard Model (SM) of particle physics. Unlike the discoveries of the top quark and Higgs boson however, searches for Beyond Standard Model (BSM) physics have much less theoretical guidance in terms of what exactly to look for and/or rule out -- or too much, depending on how one looks at it. Astrophysical evidence for the existence of non-baryonic, particulate dark matter (DM) is thus one of the biggest clues an agnostic high energy physicist might have, and has inspired a large program of searches for production of DM candidates at the LHC. Sue Ann has been involved in such searches at the Compact Muon Solenoid experiment since before it first took data at the novel center-of-mass energy of 7 TeV in 2010.

When trolling for unknown species in an ocean of fish, the game is to cast as many nets, as widely as possible. For DM production some of the most generic signatures expected in proton-proton collisions have final states consisting of only jets and apparent missing transverse momentum -- the latter from DM candidates, which leave no detector footprint. Such signatures are regarded as the most difficult to control, being highly sensitive to resolution and mismeasurement effects, as well as theoretical models of jet fragmentation. They are nevertheless some of the largest targets for BSM physics, and jet activity itself yields a rich phenomenology to be exploited for distinguishing new physics from SM backgrounds. Sue Ann’s studies in this area range from jet/missing momentum triggers, resolution and jet flavor identification, to ultra-high efficiency electron/muon/tau lepton identification techniques. Her latest work includes design of a novel jet- and top quark decay reconstruction technique so sensitive that the Standard Model (SM) associated production of top quark pairs plus a Z boson, more than 1000 times smaller in cross-section than top quark pair production, is a dominant background in a search for stop squark production. Beyond Supersymmetry, this tool can be used to measure highly collimated splittings of gluons to quark pairs, and also resolve events with multiple top quark production and decays, relevant to both Higgs boson production as well as never-before measured SM processes like the simultaneous production of four top quarks.

In the present LHC shut down, Sue Ann has also ventured into neuroscience, where hardware and analysis techniques prevalent in high energy physics may find useful applications. In particular, present advances in semiconductor and micro-fabrication technology should permit the design of a fast, single-photon imaging device totaling no more than about 1mm3 in size, which can be implanted entirely in the tissue to be imaged. Such a device can be promising for minimally invasive imaging of freely moving animals, possibly in previously inaccessible locations, and (with two devices) correlated activity in disparate regions of the brain.