Experimental tests of lepton universality in τ decay
Abstract
The branching fractions for τ-->eνντ, μνντ, and hντ are measured using data collected with the CLEO detector at the CESR e+e- collider: Be=0.1776+/-0.0006+/-0.0017, Bμ=0.1737+/-0.0008+/-0.0018, and Bh=0.1152+/-0.0005+/-0.0012, where the first error is statistical, the second systematic, and h refers to either a charged π or K. Also measured is the τ mass, mτ=(1778.2+/-1.4) MeV. Lepton universality is affirmed by the relative branching fractions (Bμ/Be=0.9777+/-0.0063+/-0.0087, Bh/Be=0.6484+/-0.0041+/-0.0060) and the charged-current gauge coupling-constant ratios (gμ/ge=1.0026+/-0.0055, gτ/gμ=0.9990+/-0.0098). The τ mass result may be recast as a τ neutrino mass limit, mντ<60 MeV at 95% C.L.
- Publication:
-
Physical Review D
- Pub Date:
- March 1997
- DOI:
- 10.1103/PhysRevD.55.2559
- Bibcode:
- 1997PhRvD..55.2559A
- Keywords:
-
- 13.35.Dx;
- 14.60.Fg;
- 14.60.Lm;
- 14.60.Pq;
- Decays of taus;
- Taus;
- Ordinary neutrinos (nuW bosons;
- Neutrino mass and mixing