Measurement of the $\ddot{I}„$-lepton lifetime at Belle

Abstract

The lifetime of the $\ddot{I}„$-lepton is measured using the process $e^{+}{e}^{-}\to \ddot{I}{„}^{+}\ddot{I}{„}^{-}$, where both $\ddot{I}„$-leptons decay to $3\ddot{I}€\hat{I}{½}_{\ddot{I}}„$. The result for the mean lifetime, based on $711{\mathrm{fb}}^{-1}$ of data collected with the Belle detector at the $\hat{I}\yen (4S)$ resonance and $60\mathrm{MeV}$ below, is $\ddot{I}„=(290.17\pm 0.53(stat.)\pm 0.33(syst.))\cdot 10^{-15}\mathrm{s}$. The first measurement of the lifetime difference between $\ddot{I}{„}^{+}$ and $\ddot{I}{„}^{-}$ is performed. The upper limit on the relative lifetime difference between positive and negative $\ddot{I}„$-leptons is $|\hat{I}”\ddot{I}„|/\ddot{I}„<7.0\times 10^{-3}$ at 90% CL.

17 pages, 4 figures. Submitted to Phys. Rev. Lett