Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fermionic dark matter via UV and IR freeze-in and its possible X-ray
  signature   Non-observation of any dark matter signature at various direct detection
experiments over the last decade keeps indicating that immensely popular WIMP
paradigm may not be the actual theory of particle dark matter. Non-thermal dark
matter produced through freeze-in is an attractive proposal, naturally
explaining null results by virtue of its feeble couplings with the Standard
Model (SM) particles. We consider a minimal extension of the SM by two gauge
singlet fields namely, a $\mathbb{Z}_2$-odd fermion $\chi$ and a pseudo scalar
$\tilde{\phi}$, where the former has interactions with the SM particles only at
dimension five level and beyond. This introduces natural suppression in the
interactions of $\chi$ by a heavy new physics scale $\Lambda$ and forces $\chi$
to be a non-thermal dark matter candidate. We have studied production of $\chi$
in detail taking into account both ultra-violate (UV), infra-red (IR) as well
as mixed UV-IR freeze-in and found that for $10^{10}{\rm GeV}\leq\Lambda\leq
10^{15}{\rm GeV}$, $\chi$ is dominantly produced via UV and mixed UV-IR
freeze-in when reheat temperature $T_{RH}\gtrsim 10^4$ GeV and below which the
production is dominated by IR and mixed freeze-in. Furthermore, we have
considered the cascade annihilation $\chi\bar{\chi} \rightarrow
\tilde{\phi}\tilde{\phi}\rightarrow 4\gamma$ to address the longstanding
$\sim3.5$ keV X-ray line observed from various galaxies and galaxy clusters. We
have found that the long-lived intermediate state $\tilde{\phi}$ modifies dark
matter density around the galactic centre to an effective density $\rho_{eff}$
which strongly depends on the decay length of $\tilde{\phi}$. Finally, the
allowed parameter space in $\Lambda-g$ plane ($g$ is the coupling between
$\chi\bar{\chi}$ and $\tilde{\phi}$) is obtained by comparing our result with
the XMM Newton observed X-ray flux from the centre of Milky Way galaxy in
$2\sigma$ range.

10
The categories of this paper are: q-bio
2
The categories of this paper are: math
28
The categories of this paper are: alg-geom
5
The categories of this paper are: gr-qc
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The categories of this paper are: hep-th
6
The categories of this paper are: astro-ph
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: comp-gas
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The categories of this paper are: cond-mat
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph