Measurements of the $\tau$ Mass and Mass Difference of the ${\tau }^{+}$ and ${\tau }^{-}$} at BaBar

Abstract

We present the result from a precision measurement of the mass of the $\tau$ lepton, $M_{\tau }$, based on $423f{b}^{-1}$ of data recorded at the ${\rm Y}(4S)$ resonance with the BaBar detector. Using a pseudomass endpoint method, we determine the mass to be $1776.68\pm 0.12(stat)\pm 0.41(syst)MeV$. We also measure the mass difference between the ${\tau }^{+}$ and ${\tau }^{-}$, and obtain $(M_{{\tau }^{+}}-M_{{\tau }^{-}})/M_{AVG}^{\tau }=(-3.4\pm 1.3(stat)\pm 0.3(syst))\times 10^{-4}$, where $M_{AVG}^{\tau }$ is the average value of $M_{{\tau }^{+}}$ and $M_{{\tau }^{-}}$.

15 pages, 10 figures, submitted to Phys. Rev. D