====== TTP96-03 Resumming Phase Space Logarithms in Inclusive Semileptonic $B$ Decays ====== We study logarithms of the form $\ln(m_q/m_b)$ which arise in the inclusive semileptonic decay of a bottom quark to a quark of mass $m_q$. We use the renormalization group to resum the leading radiative corrections to these terms, of the form $m_q^2\alpha_s^n\ln^n(m_q/m_b)$, $m_q^3\alpha_s^{n+1}\ln^n(m_q/m_b)$ and $m_q^4\alpha_s^n\ln^{n+1}(m_q/m_b)$. The first two resummations are trivial, while the latter involves a non-trivial mixing of four-fermi operators in the $1/m_b$ expansion. We illustrate this technique in a toy model in which the semileptonic decay is mediated by a vector interaction, before treating the more complicated case of left-handed decay. |**Christian Bauer, Adam Falk and Michael Luke** | |** Phys. Rev. D54 2097-2107 1996 ** | | {{preprints:1996:ttp96-03.pdf|PDF}} {{preprints:1996:ttp96-03.ps|PostScript}} [[http://arxiv.org/abs/hep-ph/9604290|arXiv]] | | |