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The lifetime of the $tau$-lepton is measured using the process $e^+e^-rightarrowtau^+tau^-$, where both $tau$-leptons decay to $3pi u_tau$. The result for the mean lifetime, based on $711,mathrm{fb}^{-1}$ of data collected with the Belle detector at the $Upsilon(4S)$ resonance and $60,mathrm{MeV}$ below, is $tau = (290.17 pm 0.53(mathrm{stat.}) pm 0.33(mathrm{syst.}))cdot10^{-15},mathrm{s}$. The first measurement of the lifetime difference between $tau^+$ and $tau^-$ is performed. The upper limit on the relative lifetime difference between positive and negative $tau$-leptons is $|Deltatau| / tau < 7.0 times 10^{-3}$ at 90% CL.
215 - K. Belous , M. Shapkin , et al. 2009
The cross sections for the reactions $e^+e^- to phieta, quad phieta, quad rhoeta, quad rhoeta$ have been measured using a data sample of 516 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. The correspondin g values of the cross sections are: $1.4 pm 0.4 pm 0.1$ fb $(phieta)$, $5.3 pm 1.1 pm 0.4$ fb $(phieta)$, $3.1 pm 0.5 pm 0.1$ fb $(rhoeta)$ and $3.3 pm 0.6 pm 0.2$ fb $(rhoeta)$. The energy dependence of the cross sections is presented using Belle measurements together with those of CLEO and BaBar.
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