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$Bto D^astell u$ at non-zero recoil

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 تاريخ النشر 2019
  مجال البحث
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The current status of the lattice-QCD calculations of the form factors of the $Bto D^astell u$ semileptonic decay is reviewed. Particular emphasis is given to the most mature calculation at non-zero recoil coming from the Fermilab Lattice and MILC collaborations. Blinded, preliminary results for the form factors are shown, including a preliminary, but detailed error budget. The lattice results seem to favor a large slope at small recoil, in contrast to the latest untagged results coming from the Belle collaboration. A comprehensive comparison between the latest BGL $z$ expansions of Belle, Babar, the lattice and a joint BGL fit including lattice and Belle data is presented, and a roadmap to improve the current calculation is discussed. The current implications for $V_{cb}$ and $R(D^ast)$ are discussed.



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We present preliminary blinded results from our analysis of the form factors for $Brightarrow D^astell u$ decay at non-zero recoil. Our analysis includes 15 MILC asqtad ensembles with $N_f=2+1$ flavors of sea quarks and lattice spacings ranging from $aapprox 0.15$ fm down to $0.045$ fm. The valence light quarks employ the asqtad action, whereas the $b$ and $c$ quarks are treated using the Fermilab action. We discuss the impact that our results will have on $left|V_{cb}right|$ and $R(D^ast)$.
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