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تسجيل مستخدم جديدMeasurement of the Michel Parameter xi in Polarized Muon Decay and Implications on Exotic Couplings of the Leptonic Weak Interaction
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The Michel parameter xi has been determined from a measurement of the longitudinal polarization of positrons emitted in the decay of polarized and depolarized muons. The result, xi = 0.981 +- 0.045stat +- 0.003syst, is consistent with the Standard Model prediction of unity, and provides an order of magnitude improvement in the relative precision of this parameter. This value sets new constraints on exotic couplings beyond the dominant V-A description of the leptonic weak interaction.
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We present the first measurement of the Michel parameters $bar{eta}$ and $xikappa$ in the radiative leptonic decay of the $tau$ lepton using 703 f$mathrm{b}^{-1}$ of data collected with the Belle detector at the KEKB $e^+e^-$ collider. The Michel par
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