Higgs Boson

Before entering medical physics research, I previously studied experimental particle physics. I analyzed data recorded by the ATLAS experiment - one of the four detectors positioned on the Large Hadron Collider (LHC) at CERN. Working in collaboration with physicists from around the world, I measured high-energy proton-proton collisions in order to search for evidence of a fundamental particle of nature called the Higgs boson. Here is a TED video and a PhD Comics animation that do a great job of explaining the physics behind the Higgs boson. You can also find a "flash talk" I gave at the Oxford Physics Department in 2013.

I focussed on searching for events where the Higgs boson decays to two W bosons, which in turn can each decay to either an electron and a neutrino or a muon and a neutrino. It is these electrons and muons that we detect with the ATLAS detector. Selecting events where a Higgs boson has decayed and rejecting other background processes that give the same experimental signature is a difficult task, both experimentally and theoretically. The Higgs to WW search is particularly challenging because it is not possible to reconstruct the mass of the Higgs boson from its decay products, making it very difficult to discriminate between signal and background. Nonetheless, the analysis played a vital role in the discovery of the Higgs boson announced in July 2012. My personal contributions improved the theoretical predictions of the signal and background processes in order to yield a more sensitive analysis. These were the dominant sources of uncertainty in this search.

Following the Higgs boson discovery, we then aimed to show that this particle had the properties predicted by theory. By using the entire dataset and making numerous refinements, the ATLAS H→WW analysis yielded the most precise measurement of the Higgs boson production cross section made during Run-I of the LHC. This final version of the analysis became my thesis.

During my first postdoc position at Oxford University, I adjusted the H→WW analysis to infer the underlying kinematic distributions of the Higgs boson by deconvolving detector effects using an iterative Bayesian approach. This has been published here.


ATLAS Collaboration, Phys. Rev. D 92 (2015) 012006