Jet Substructure & Boosted Objects

For the first time in the history of particle physics, the collision energy of a particle collider is well above the scale of electroweak symmetry breaking. Consequently, massive particles produced in these collisions, such as W and Z bosons, top quarks, and even the Higgs boson, may have significant momentum, such that their decay products - most often quarks and gluons - are collimated due to the Lorentz-boost in the laboratory frame. New techniques, algorithms, and even instrumentation are required to study these objects, and to use them to search for signs of physics beyond the Standard Model.

Approach

We have spearheaded the adoption of algorithms that allow for more precise and useful analysis of the internal structure of jets than ever before. This allows for details measurements and integration of the resulting observables into methods for signal and background discrimination.
Measurements and performance analyses are crucial for this endeavor. We have studied boosted W bosons (ATL-PHYS-PUB-2015-033), and , looked at the enhancements due to quark emissions of a W boson (arXiv:1609.07045) and measured the soft drop jet mass (arXiv:1711.08341)
Crucially, this endeavor relies on a deep understanding of the hadronic calorimeter itself, including its response to single isolate hadrons.
Our group is now pursuing complex reconstruction methods that leverage the tool box of Deep Learning algorithms to improve calorimeter energy reconstruction and particle identification.