Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Gauge Invariance of the Muonium-Antimuonium Oscillation Time Scale and
  Limits on Right-Handed Neutrino Masses   The gauge invariance of the muonium-antimuonium ($M\bar{M}$) oscillation time
scale is explicitly demonstrated in the Standard Model modified only by the
inclusion of singlet right-handed neutrinos and allowing for general
renormalizable interactions. The see-saw mechanism is exploited resulting in
three light Majorana neutrinos and three heavy Majorana neutrinos with mass
scale $M_R\gg M_W$. The leading order matrix element contribution to the
$M\bar{M}$ oscillation process is computed in $R_\xi$ gauge and shown to be
$\xi$ independent thereby establishing the gauge invariance to this order.
Present experimental limits resulting from the non-observation of the
oscillation process sets a lower limit on $M_R$ roughly of order 600 GeV.

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The categories of this paper are: supr-con
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The categories of this paper are: q-fin
5
The categories of this paper are: gr-qc
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The categories of this paper are: funct-an
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The categories of this paper are: cs
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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
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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: alg-geom