Publication at Faculty of Mathematics and Physics |
2023
Abstract
We present a measurement of the τ-lepton mass using a sample of about 175 million eþe− → τþτ− events collected with the Belle II detector at the SuperKEKB eþe− collider at a center-of-mass energy of 10.579 GeV. This sample corresponds to an integrated luminosity of 190 fb−1.
We use the kinematic edge of the τ pseudomass distribution in the decay τ− → π−πþπ−ντ and measure the τ mass to be 1777.09 0.08 0.11 MeV=c2, where the first uncertainty is statistical and the second systematic. This result is the most precise to date.