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Published January 1, 1996 | Published
Journal Article Open

Measurement of the mass of the τ lepton


A data-driven energy scan in the immediate vicinity of the τ pair production threshold has been performed using the Beijing Spectrometer at the Beijing Electron-Positron Collider. Approximately 5 pb^(-1) of data, distributed over 12 scan points, have been collected. A previous mass value for the τ lepton, obtained using only the eμ final state, has been published. In this paper, the final BES result on the mass measurement is presented. The analysis is based on the combined data from the ee, eμ, eh, μμ, μh, and hh final states, where h denotes a charged π or K. A maximum likelihood fit to the τ pair production cross section data yields the value m_τ=1776.96_(-0.21)-0.17^(+0.18+0.25) MeV.

Additional Information

© 1996 The American Physical Society. Received 25 July 1995; published in the issue dated 1 January 1996. The BES Collaboration would like to thank the staffs of the BEPC accelerator and the Computing Center at the Institute of High Energy Physics, Beijing, for their outstanding efforts, and also Y. S. Tsai for helpful discussions about the T^+T^- cross section near threshold. The work of the BES Collaboration was supported in part by the National Natural Science Foundation of China under Contract No. 19290400 and the Chinese Academy of Sciences under Contract NO. KJ85 (IHEP), by the Department of Energy under Contracts No. DE-FG02.91ER40676 (Boston University), DE-FG03-92ER40701 (California Institute of Technology), DEFG03-93ER40788 (Colorado State University), DE-AC02-76ER03069 (MIT), DE-AC03- 76SF00515 (SLAC), DE-FG03-91ER40679 (University of California at Irvine), DE-FG03-94ER40833 (University of Hawaii), DE-FG05-92ER40736 (University of Texas at Dallas), DE-AC35-89ER40486 (SSC Lab), by the U.S. National Science Foundation, Grant No. PHY9203212 (University of Washington), and by the Texas National Research Laboratory Commission under Contracts Nos. RGFYQlB5, RGFY92B5 (Colorado State), and RCFY93-316H (University of Texas at Dallas).

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