SU(2) gauge theory with $N_f=24$ massless fermions is noninteracting at long distances, i.e., it has an infrared fixed point at vanishing coupling. With massive fermions, the fermions are expected to decouple at energy scales below the fermion mass, and the infrared behavior is that of confining SU(2) pure gauge theory. We demonstrate this behavior nonperturbatively with lattice Monte Carlo simulations by measuring the gradient flow running coupling.

• Received 23 November 2021
• Revised 2 April 2022
• Accepted 29 August 2022

DOI:https://doi.org/10.1103/PhysRevLett.129.131601

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Published by the American Physical Society