Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Hanbury Brown--Twiss Interferometry and Collectivity in Small Systems   Hanbury Brown--Twiss interferometry (HBT) provides crucial insights into both
the space-time structure and the momentum-space evolution of ultrarelativistic
nuclear collisions at freeze-out. In particular, the dependence of the HBT
radii on the transverse pair momentum $K_T$ and the system charged multiplicity
$dN_{\mathrm{ch}}/d\eta$ may reflect the mechanisms driving collective behavior
in small systems. This paper argues that certain features observed in the
multiplicity dependence of the HBT radii can be naturally understood if small
systems evolve hydrodynamically at high-multiplicity. This study thus
establishes a baseline for the multiplicity dependence of HBT in hydrodynamics
which may prove useful in discriminating between competing models of
collectivity in nuclear collisions.

18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
26
The categories of this paper are: bayes-an
8
The categories of this paper are: hep-ex
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
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The categories of this paper are: chao-dyn
16
The categories of this paper are: stat