Sébastien Rettie

Dr. Sébastien Rettie

email

NSERC Postdoctoral Research Fellow

Department of Physics & Astronomy
University College London
ATLAS Group

My research interests lie in the area of experimental high-energy particle physics. Particle physics studies the fundamental building blocks of the universe and their interactions with each other. More precisely, I am a member of the ATLAS Experiment at the Large Hadron Collider (LHC) at CERN. The ATLAS experiment consists of an international collaboration of over 3000 scientists working together to explore physics at the TeV energy scale, where new physical phenomena are expected to appear. The ATLAS detector is a multipurpose particle detector located in Geneva, Switzerland.

In 2012, the ATLAS collaboration announced the discovery of a new particle consistent with the Higgs boson. The next logical step of the physics program at the LHC is to precisely measure the properties of this newly observed particle. To this end, I am working on measuring the properties of the Higgs boson. In particular, the measurement of the transverse momentum spectrum of the Higgs boson is my main focus. I am also investigating the use of machine learning techniques to improve the b-tagging and tracking capabilities of the ATLAS detector.

During my undergraduate and graduate studies, I searched for physics beyond the standard model. More particularly, I have worked with the ATLAS supersymmetry group as an undergraduate research assistant, and actively contributed to the Z' search efforts at the LHC during my graduate studies under the supervision of Oliver Stelzer-Chilton. The specific signature I looked for during my Ph. D. was that of a Z' candidate decaying into two leptons (either two electrons or two muons) in the final state. In addition, I currently serve as the liaison between the ATLAS Exotics and the Muon Combined Performance groups. In order to gain hardware experience, I was part of the group aiming to characterize small-strip Thin Gap Chambers for the New Small Wheel upgrade of the ATLAS detector. I also contributed to the muon trigger group as an editor of the full Run 2 publication, and evaluated the performance of the ATLAS detector by measuring muon trigger efficiencies for high-momentum muons.