Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Observation of $\rho / \omega$ Meson Modification in Nuclear Matter   We have measured invariant mass spectra of electron-positron pairs in the
target rapidity region of 12GeV p+A reactions. We have observed a significant
difference in the mass spectra below the $\omega$ meson between p+C and p+Cu
interactions. The difference is interpreted as a signature of the $\rho/\omega$
modification at normal nuclear-matter density.

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The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
33
The categories of this paper are: plasm-ph
14
The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
27
The categories of this paper are: comp-gas