More information about some of my past and current research directions.
The Higgs field plays a central role in the Standard Model: its potential has a shape such that the Higgs field acquires a vacuum expectation value which spontaneously breaks the electroweak gauge symmetry of the Standard Model, leading to the disparate nature of the fundamental forces we see at low energies. In parallel, this vacuum expectation value gives masses to the Standard Model fermions via its Yukawa couplings. The values of the Higgs couplings are thus responsible for a great deal of the structure we see in the Universe, and testing the consistency of this theory is of paramount importance in particle physics.
Moreover, there are deep, theoretical reasons to believe that the Higgs is related to physics beyond the Standard Model that would appear at or around the TeV scale. These reasons make up the (Electroweak) Hierarchy Problem: according to our best notions of effective field theory, we should not expect scalar fields to appear with masses parametrically smaller than the cutoff of the theory (where new, microsopic physics would come into play). This is exemplified in all concrete models that predict the Higgs mass: if the new physics is much heavier than the electroweak scale, a significant amount of “fine-tuning” of the parameters of the theory is required to reproduce the observed Standard Model.
For all these reasons, it is crucial to test the Higgs sector of the Standard Model at the Large Hadron Collider (LHC) and future machines. A significant portion of my research is in this direction: both in constructing models of BSM physics related to the Higgs and understanding their signatures at collider experiments, and in performing detailed calculations necessary to interpret experimental measurements as constraints on BSM couplings of the Higgs.
Since 2020 I have been heavily involved in studying the unique physics case of a high-energy muon collider. As a heavier cousin of the electron, muons can be more readily accelerated to high energies without the barrier of synchrotron radiation, and while still being elementary particles whose full energy is available in the collision. There are significant challenges in accelerating muon beams, but these advantages offer a potentially much more efficient route to very high energy scales beyond the horizon of the LHC. A muon collider inscribed roughly inside the Fermilab campus, for instance, could reach center of mass energies of 8 – 10 TeV, providing a direct reach comparable to an 80 TeV proton collider.
My research has focussed on some of the unique signatures that are possible with high-energy muon collisions. At these energies, there are large cross sections for vector-boson-scattering processes. These provide unprecedented sensitivity to the electroweak-Higgs interactions, the mechanism of electroweak symmetry breaking, and even to new sources of CP-violation1. My collaborators and I have also shown that a high-energy muon collider would have incomparable sensitivity to new sources of lepton flavor violation as well 2 3. There is a great deal more work needed in realizing a Muon Collider; more details and information on getting involved in the broader effort can be found on the U.S. Muon Collider Collaboration (USMCC) website.
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“Barr–Zee Diagrams at a High-Energy Muon Collider”,
SDH, J. Lodman, A. Parikh and M. Reece,
JHEP 12 (2024) 134, arXiv:2410.01873 ↩
“Lepton Flavor Violation: From Muon Decays to Muon Colliders”,
P. Asadi, H. Bagherian, K. Fraser, SDH and Q. Lu,
Phys. Rev. D 113 (2026), arXiv:2509.22771. ↩
“Complementary Signals of Lepton Flavor Violation at a High-Energy Muon Collider”,
SDH, Q. Lu and M. Reece,
JHEP 07 (2022) 036, arXiv:2203.08825. ↩