We compute the running of the coupling in SU(2) gauge theory with six fermions in the fundamental representation of the gauge group. We find a strong evidence that this theory has an infrared stable fixed point at strong coupling and measure also the anomalous dimension of the fermion mass operator at the fixed point. This theory therefore likely lies close to the boundary of the conformal window and will display novel infrared dynamics if coupled with the electroweak sector of the Standard Model.

We study the evolution of the coupling in SU(2) gauge field theory with N f = 8 fundamental fermion flavors on the lattice. This model is expected to have an infrared fixed point at high coupling. We use HEX-smeared Wilson-clover action, and measure the gradient flow running coupling with Dirichlet boundary conditions. Extrapolating our results to continuum, we find an infrared fixed point at g 2 * = 8.24 (59) +0.97 −1.64 , with statistical and systematic error estimates. We also measure the anomalous dimension of the quark mass operator, and find its value at the fixed point γ * 0.15 ± 0.02, although for this quantity a reliable continuum limit is still lacking.

We study the running of the coupling in SU(2) gauge theory with 8 massless fundamental representation fermion flavours, using the gradient flow method with Schrödinger functional boundary conditions. Gradient flow allows us to measure robust continuum limit for the step scaling function. The results show a clear indication of infrared fixed point consistent with perturbation theory.