Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Recent Highlights from the PHENIX Heavy-Ion Program at RHIC   Over the last decade it has been established that a quark-gluon plasma (QGP)
is formed in ultrarelativistic A+A collisions at RHIC energies. In recent
years, detector upgrades have enabled the detailed study of this hot and dense
matter. Important probes, among others, are direct photons and heavy flavor
observables. Although the RHIC d+Au program was originally undertaken to study
initial state and cold nuclear matter effects, recent measurements at both RHIC
(d+Au) and the LHC (p+Pb) have found evidence for collective phenomena in these
small systems.

6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex