Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Search for pairs of highly collimated photon-jets in $pp$ collisions at
  $\sqrt{s}$ = 13 TeV with the ATLAS detector   Results of a search for the pair production of photon-jets$-$collimated
groupings of photons$-$in the ATLAS detector at the Large Hadron Collider are
reported. Highly collimated photon-jets can arise from the decay of new, highly
boosted particles that can decay to multiple photons collimated enough to be
identified in the electromagnetic calorimeter as a single, photonlike energy
cluster. Data from proton-proton collisions at a center-of-mass energy of 13
TeV, corresponding to an integrated luminosity of 36.7 fb$^{-1}$, were
collected in 2015 and 2016. Candidate photon-jet pair production events are
selected from those containing two reconstructed photons using a set of
identification criteria much less stringent than that typically used for the
selection of photons, with additional criteria applied to provide improved
sensitivity to photon-jets. Narrow excesses in the reconstructed diphoton mass
spectra are searched for. The observed mass spectra are consistent with the
Standard Model background expectation. The results are interpreted in the
context of a model containing a new, high-mass scalar particle with narrow
width, $X$, that decays into pairs of photon-jets via new, light particles,
$a$. Upper limits are placed on the cross section times the product of
branching ratios $\sigma \times \mathcal{B}(X \rightarrow aa) \times \mathcal
{B}(a \rightarrow \gamma \gamma)^{2}$ for 200 GeV $< m_{X} <$ 2 TeV and for
ranges of $ m_a $ from a lower mass of 100 MeV up to between 2 and 10 GeV,
depending upon $ m_X $. Upper limits are also placed on $\sigma \times
\mathcal{B}(X \rightarrow aa) \times \mathcal {B}(a \rightarrow 3\pi^{0})^{2}$
for the same range of $ m_X $ and for ranges of $ m_a $ from a lower mass of
500 MeV up to between 2 and 10 GeV.

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The categories of this paper are: bayes-an
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The categories of this paper are: supr-con
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The categories of this paper are: patt-sol
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: dg-ga
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: math
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The categories of this paper are: comp-gas
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The categories of this paper are: astro-ph
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The categories of this paper are: nucl-th