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Heavy Quark Expansion for the Inclusive Decay $\bar B\toτ\,\barν\,X$

Adam F. Falk·Zoltan Ligeti·Matthias Neubert·Yosef Nir
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Abstract

We calculate the differential decay rate for inclusive $\bar B\toτ\,\barν\,X$ transitions to order $1/m_b^2$ in the heavy quark expansion, for both polarized and unpolarized tau leptons. We show that using a systematic $1/m_b$ expansion significantly reduces the theoretical uncertainties in the calculation. We obtain for the total branching ratio ${\rm BR}(\bar B\toτ\,\barν\,X)=2.30\pm 0.25\%$, and for the tau polarization $A_{\rm pol}=-0.706\pm0.006$. {}From the experimental measurement of the branching ratio at LEP, we derive the upper bound $\lo\leq 0.8\gev^2$ for one of the parameters of the heavy quark effective theory.

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Adam F. Falk, Zoltan Ligeti, Matthias Neubert, Yosef Nir. 1994-01-10. Heavy Quark Expansion for the Inclusive Decay $\bar B\toτ\,\barν\,X$. https://doi.org/10.1016/0370-2693(94)91206-8

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