The seminar presents a new high-precision measurement of the B0 effective lifetime in B0 to J/psi K*0 decays, using 140 fb-1 of 13 TeV pp collision data recorded by the ATLAS detector. Results for the average decay width, Gamma_d, and the width ratio Gamma_d/Gamma_s are also reported. The experimental methodologies and systematic uncertainty evaluations are described in detail and implications of the results for heavy-flavor effective theories are discussed.

Refreshments will be served at 10:30