# Leendert Hayen

Research Assistant Professor

Riddick Hall 160

### Bio

Dr. Hayen received his M.S. in Physics summa cum laude from KU Leuven University, Belgium, and through the Erasmus program at ETH Zuerich, Switzerland. He went on to earn his PhD in 2018 from KU Leuven under the supervision of Prof. Nathal Severijns, with both an experimental and theoretical focus on understanding beta spectroscopy in search for exotic physics in the electroweak interaction. He also pioneered an accurate treatment of forbidden beta decays in the reactor antineutrino anomaly, and developed Monte Carlo methods to propagate their uncertainty. He then joined Dr. Albert Young’s group as a research assistant professor at North Carolina State University and Triangle Universities Nuclear Laboratory in 2019.

### Research Description

Leendert’s research lies at the overlap between nuclear, neutrino and low-energy particle physics, with a specific focus on fundamental symmetry tests. He developed the most precise description of nuclear beta decay spectra together with open-source software which is being used by experiments over the world, from precision beta spectroscopy to dark matter searches. He is currently involved in several experimental campaigns using novel techniques to measure the beta spectrum shape, and using ultra cold neutrons to measure their lifetime and angular correlations afte decay. Additionally, he is interested in theoretical topics adjecent to beta decay, such as electroweak radiative corrections and atomic interference effects.

### Selected Publications

High precision analytical description of the allowed $\beta$ spectrum shape
Leendert Hayen, Nathal Severijns, Kazimierz Bodek, Dagmara Rozpedzik, Xavier Mougeot
Reviews of Modern Physics, 90 015008, (2018), doi:10.1103/RevModPhys.90.015008

First-forbidden transitions in the reactor anomaly
Leendert Hayen; Joel Kostensalo; Nathal Severijns; Jouni Suhonen
Physical Review C, 100 054323, (2019), doi:10.1103/PhysRevC.100.054323

Beta Spectrum Generator: High precision allowed $\beta$ spectrum shapes
Leendert Hayen, Nathal Severijns
Computer Physics Communications, 241 152, (2019), 152-164, doi:10.1016/j.cpc.2019.02.012

Measurement of the permanent electric dipole moment of the neutron
C. Abel et al. (nEDM collaboration)
Physical Review Letters, 124 081803, (2020), doi:10.1103/PhysRevLett.124.081803