Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Leptonic widths of heavy quarkonia: QCD/NRQCD matching for the
  electromagnetic current at O(\alpha_s v^2)   We construct the S-wave part of the electromagnetic vector annihilation
current to $O(\alpha_s v^2)$, where $v$ is the non-relativistic quark velocity,
for heavy quarks whose dynamics are described by the NRQCD action on the
lattice. The NRQCD vector current for $Q\bar{Q}$ annihilation is expressed as a
linear combination of lattice operators with quantum numbers L=0, $J^P=1^-$,
and the coefficients are determined by matching to the corresponding continuum
current in QCD to$O(v^2)$ at one-loop. The annihilation channel gives a complex
amplitude with Coulomb-exchange and infrared singularities, making a careful
choice for the contours of integration and infrared subtraction functions in
the numerical integration necessary. An automated vertex generation program
written in Python is employed, allowing us to use a realistic NRQCD action and
an improved gluon lattice action; a change in the definition of either action
is easily accommodated in this procedure. The final result is applicable to
simulations of electromagnetic decays of heavy quarkonia, notably the
$\Upsilon$ meson.

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The categories of this paper are: alg-geom
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: gr-qc
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: econ
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The categories of this paper are: physics
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph