Maximal-isospin two- and three-body amplitudes at physical quark masses

In two publications, led by Steve Sharpe (UW, co-PI), in collaboration with Sebastian Dawid (UW), Zach Draper (UW), Andrew Hanlon (Kent State U. and Hampton U.), Ben Hörz (Intel DE), Colin Morningstar (CMU), Fernando Romero-López (Bern U.), and Sarah Skinner (CMU), we determine, for the first time, three-particle scattering amplitudes with physical quark masses. These amplitudes derive from the finite-volume spectra of systems of two and three mesons obtained using lattice QCD calculations. Our results involve combinations of pions and kaons at a lattice spacing of $a = 0.063\text{~fm}$ and in the isospin-symmetric limit. We also present accurate results for maximal-isospin two-meson amplitudes, with those for maximal isospin pion + kaon and two kaon systems being the first determinations at the physical point. Dense lattice spectra are produced using the stochastic Laplacian-Heaviside method, and the analysis leading to scattering amplitudes is conducted using the relativistic finite-volume formalism. Results are compared to chiral perturbation theory and to phenomenological fits to experimental data, showing good agreement.

Papers: Phys. Rev. Lett. 135 (2025), 021903; Phys. Rev. D 112 (2025), 014505