Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The ratio $\mathcal{R}(D_s)$ for $B_s \to D_s \ell\nu_\ell$ by using the
  QCD light-cone sum rules within the framework of heavy quark effective field
  theory   In the paper, we study the $B_s\to D_s$ transition form factors by using the
light-cone sum rules within the framework of heavy quark effective field
theory. We adopt a chiral current correlation function to do the calculation,
the resultant transition form factors $f_+^{B_s\to D_s}(q^2)$ and $f_0^{B_s\to
D_s}(q^2)$ are dominated by the contribution of $D_s$-meson leading-twist
distribution amplitude, while the contributions from less certain $D_s$-meson
twist-3 distribution amplitudes are greatly suppressed. At the largest recoil
point, we obtain $f_{+,0}^{B_s \to D_s}(0)=0.533^{+0.112}_{-0.094}$. By further
extrapolating the transition form factors into all the physically allowable
$q^2$ region with the help of the $z$-series parametrization approach, we
calculate the branching fractions $\mathcal{B}(B_s \to D_s \ell^\prime
\nu_{\ell^\prime})$ with $(\ell^\prime= e,\mu)$ and $\mathcal{B}(B_s \to D_s
\tau \nu_\tau)$, which gives $\mathcal{R}(D_s)=0.334\pm 0.017$.

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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: q-alg
18
The categories of this paper are: econ
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The categories of this paper are: q-fin
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The categories of this paper are: comp-gas
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The categories of this paper are: nucl-ex
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: ao-sci
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The categories of this paper are: bayes-an
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: cs
2
The categories of this paper are: math