Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of Lambda H-4 hyperhydrogen by decay-pion spectroscopy in
  electron scattering   At the Mainz Microtron MAMI, the first high-resolution pion spectroscopy from
decays of strange systems was performed by electron scattering off a Be-9
target in order to study the ground-state masses of Lambda-hypernuclei.
Positively charged kaons were detected by a short-orbit spectrometer with a
broad momentum acceptance at zero degree forward angles with respect to the
beam, efficiently tagging the production of strangeness in the target nucleus.
In coincidence, negatively charged decay-pions were detected by two independent
high-resolution spectrometers. About 10^3 pionic weak decays of hyperfragments
and hyperons were observed. The pion momentum distribution shows a
monochromatic peak at p_pi ~ 133 MeV/c, corresponding to the unique signature
for the two-body decay of hyperhydrogen Lambda H-4 -> He-4 + pi-, stopped
inside the target. Its binding energy was determined to be B_Lambda = 2.12 +-
0.01 (stat.) +- 0.09 (syst.) MeV with respect to the H-3 + Lambda mass.

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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: alg-geom
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The categories of this paper are: atom-ph
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The categories of this paper are: hep-th
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The categories of this paper are: bayes-an
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The categories of this paper are: astro-ph
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: math
5
The categories of this paper are: gr-qc
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The categories of this paper are: comp-gas
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol