Physical Review D 73,11 (2006) 112005;
We test whether or not the tau lepton manifests the same couplings as the mu lepton by investigating the relative decay rates in purely leptonic D+ meson decays. We use 281 pb(-1) of data accumulated at the psi(3770) resonance with the CLEO-c detector, to limit B(D+->tau(+)nu)< 2.1x10(-3) at 90% confidence level (C.L.), thus allowing us to place the first upper limit on the ratio R=Gamma(D+->tau(+)nu)/Gamma(D+->mu(+)nu). The ratio of R to the standard model expectation of 2.65 then is < 1.8 at 90% C.L., consistent with the prediction of lepton universality.
qed radiative-corrections;; universal monte-carlo;; rich detector;; b-mesons;; decays;; photos
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