Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Constraints on Light Dark Matter and U bosons, from psi, Upsilon, K+,
  pi0, eta and eta' decays   Following searches for photinos and very light gravitinos in invisible decays
of psi and Upsilon, we discuss new limits on Light Dark Matter and U bosons,
from psi and Upsilon decays, as well as rare decays of K+ and invisible decays
of pi0, eta and eta' ... . The new limits involving the vector couplings of the
U to quarks turn out, not surprisingly, to be much less restrictive than
existing ones on axial couplings, from an axionlike behavior of a light U
boson, tested in psi --> gamma U, Upsilon --> gamma U and K+ --> pi+ U decays
(or as compared to the limit from parity-violation in atomic physics, in the
presence of an axial coupling to the electron). Altogether the hypothesis of
light U bosons, and light dark matter particles, remains compatible with
particle physics constraints, while allowing for the appropriate annihilation
cross sections required, both at freeze-out (for the relic abundance) and
nowadays (if e+ from LDM annihilations are at the origin of the 511 keV line
from the galactic bulge).

34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
12
The categories of this paper are: nucl-th
4
The categories of this paper are: cond-mat
6
The categories of this paper are: astro-ph
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
32
The categories of this paper are: atom-ph
27
The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin