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arXiv · 1611.01987

$B_c$ decays from highly improved staggered quarks and NRQCD

Brian Colquhoun·Christine Davies·Jonna Koponen·Andrew Lytle·Craig McNeile
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Abstract

We calculate semileptonic form factors for the decays $B_c \to \eta_c \, l \nu$ and $B_c \to J/\psi \, l \nu$ over the entire $q^2$ range, using a highly improved lattice quark action for charm at several lattice spacings down to $a=0.045$ fm. We have two ways of treating the $b$ quark: either with an $O(\alpha_s)$ improved NRQCD formalism or by extrapolating a heavy mass $m_h$ to $m_b$ in the relativistic formalism. Comparison of the two approaches provides an important cross-check of methodologies in lattice QCD. Nonperturbative renormalisation of the currents in the relativistic theory also allows us then to fix NRQCD-charm normalisation for $b$ to $c$ decays such as $B \to D$ and $B \to D^*$.

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Brian Colquhoun, Christine Davies, Jonna Koponen, Andrew Lytle, Craig McNeile. 2016-11-07. $B_c$ decays from highly improved staggered quarks and NRQCD. https://arxiv.org/abs/1611.01987

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