Measurement of the 2S(1/2)-8D(5/2) Transition in Hydrogen

We present a measurement of the hydrogen 2S(1/2) - 8D(5/2) transition performed with a cryogenic atomic beam. The measured resonance frequency is nu = 770649561570.9(2.0) kHz, which corresponds to a relative uncertainty of 2.6 x 10(-12). Combining our result with the most recent measurement of the 1S - 2S transition, we find a proton radius of r(p) = 0.8584(51) fm and a Rydberg constant of R-infinity = 10973731.568332(52) m(-1). This result has a combined 3.1 sigma disagreement with the Committee on Data for Science and Technology (CODATA) 2018 recommended value.