Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Lifetime and population of the 2S state in muonic protium and deuterium   Radiative deexcitation (RD) of the metastable 2S state of muonic protium and
deuterium atoms has been observed. In muonic protium, we improve the precision
on lifetime and population (formation probability) values for the short-lived
{\mu}p(2S) component, and give an upper limit for RD of long-lived {\mu}p(2S)
atoms. In muonic deuterium at 1 hPa, 3.1 +-0.3 % of all stopped muons form
{\mu}d(2S) atoms. The short-lived 2S component has a population of 1.35 +0.57
-0.33 % and a lifetime of {\tau}_short({\mu}d) = 138 +32 -34 ns. We see
evidence for RD of long-lived {\mu}d(2S) with a lifetime of {\tau}_long({\mu}d)
= 1.15 +0.75 -0.53 {\mu}s. This is interpreted as formation and decay of
excited muonic molecules.

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The categories of this paper are: nucl-th
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The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
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The categories of this paper are: q-fin
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg