Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Exciting Dark Matter and the INTEGRAL/SPI 511 keV signal   We propose a WIMP candidate with an ``excited state'' 1-2 MeV above the
ground state, which may be collisionally excited and de-excites by e+e- pair
emission. By converting its kinetic energy into pairs, such a particle could
produce a substantial fraction of the 511 keV line observed by INTEGRAL/SPI in
the inner Milky Way. Only a small fraction of the WIMPs have sufficient energy
to excite, and that fraction drops sharply with galactocentric radius,
naturally yielding a radial cutoff, as observed. Even if the scattering
probability in the inner kpc is << 1% per Hubble time, enough power is
available to produce the ~3x10^42 pairs per second observed in the Galactic
bulge. We specify the parameters of a pseudo-Dirac fermion designed to explain
the positron signal, and find that it annihilates chiefly to e+e- and freezes
out with the correct relic density. We discuss possible observational
consequences of this model.

32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
15
The categories of this paper are: nucl-ex
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
16
The categories of this paper are: stat
31
The categories of this paper are: ao-sci
4
The categories of this paper are: cond-mat
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The categories of this paper are: eess
12
The categories of this paper are: nucl-th
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int