Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Neutron electric dipole moment using $N_f{=}2{+}1{+}1$ twisted mass
  fermions   We evaluate the neutron electric dipole moment $\vert \vec{d}_N\vert$ using
lattice QCD techniques. The gauge configurations analyzed are produced by the
European Twisted Mass Collaboration using $N_f{=}2{+}1{+}1$ twisted mass
fermions at one value of the lattice spacing of $a \simeq 0.082 \ {\rm fm}$ and
a light quark mass corresponding to $m_{\pi} \simeq 373 \ {\rm MeV}$. Our
approach to extract the neutron electric dipole moment is based on the
calculation of the $CP$-odd electromagnetic form factor $F_3(Q^2)$ for small
values of the vacuum angle $\theta$ in the limit of zero Euclidean momentum
transfer $Q^2$. The limit $Q^2 \to 0$ is realized either by adopting a
parameterization of the momentum dependence of $F_3(Q^2)$ and performing a fit,
or by employing new position space methods, which involve the elimination of
the kinematical momentum factor in front of $F_3(Q^2)$. The computation in the
presence of a $CP$-violating term requires the evaluation of the topological
charge ${\cal Q}$. This is computed by applying the cooling technique and the
gradient flow with three different actions, namely the Wilson, the Symanzik
tree-level improved and the Iwasaki action. We demonstrate that cooling and
gradient flow give equivalent results for the neutron electric dipole moment.
Our analysis yields a value of $\vert \vec{d}_N\vert=0.045(6)(1)\ \bar{\theta}
\ e \cdot {\rm fm}$ for the ensemble with $m_\pi=373$ MeV considered.

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The categories of this paper are: math
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
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The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci