Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Search for $\alpha$ decay of naturally occurring Hf-nuclides using a
  Cs$_2$HfCl$_6$ scintillator   Residual radioactive contaminants of a caesium hafnium chloride
(Cs$_2$HfCl$_6$) crystal scintillator have been measured in a low background
setup at the Gran Sasso National Laboratory of the INFN, Italy. The total alpha
activity of the detector is at the level of 7.8(3) mBq/kg. The results of
direct studies of the $\alpha$ decay of naturally occurring Hf isotopes that
have been performed using the "source=detector" approach are presented. In 2848
h of data taking, the $\alpha$ decay of $^{174}$Hf was observed with T$_{1/2} =
(7.0\pm1.2)\times10^{16} $ y.

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The categories of this paper are: gr-qc
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The categories of this paper are: patt-sol
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The categories of this paper are: nlin
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The categories of this paper are: chao-dyn
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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The categories of this paper are: math-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: q-bio
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The categories of this paper are: supr-con
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The categories of this paper are: cs
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-lat