PHYSICAL REVIEW D 108, 032006 (2023)

ISSN: 2470-0029, SCIE

Measurement of the τ-lepton mass with the Belle II experiment

The Belle II collaboration (I. Adachi, ..., N. Anh Ky, ...)

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.

DOI: DOI: 10.1103/PhysRevD.108.032006