Indirect Detection of Kaluza-Klein Dark Matter

TL;DR

The paper assesses indirect detection prospects for the LKP $B^{(1)}$ dark matter in Universal Extra Dimensions by computing gamma-ray, neutrino, and synchrotron fluxes from $B^{(1)}$ annihilation in the Galactic halo. It combines DM-density profiles, fragmentation functions, and non-relativistic annihilation cross sections to predict observable spectra, and then contrasts them with existing data and near-future sensitivities, isolating the dependence on the line-of-sight $J$-factor. For a Navarro–Frenk–White profile, synchrotron constraints yield a lower bound of $M \\gtrsim 0.3$ TeV, while gamma-ray observations could probe up to about $M \\sim 0.6$ TeV; neutrino limits remain weaker unless a central spike is present. The results highlight the critical role of the DM density profile and Galactic magnetic field in indirect detection and note that a GC spike would dramatically tighten constraints, whereas in its absence TeV-scale KK DM remains viable.

Abstract

We investigate prospects for indirect detection of Kaluza--Klein dark matter, focusing on the annihilation radiation of the first Kaluza--Klein excitation of the Hypercharge gauge boson $B^{(1)}$ in the Galactic halo, in particular we estimate neutrino, gamma-ray and synchrotron fluxes. Comparing the predicted fluxes with observational data we are able to constrain the $B^{(1)}$ mass (and therefore the compactification scale). The constraints depend on the specific model adopted for the dark matter density profile. For a NFW profile the analysis of synchrotron radiation puts a lower bound on the $B^{(1)}$ mass of the order of $\simeq 300$ GeV.

Figures (9)

• Figure 1: Fragmentation function of different quark species into pions. From bottom to top, the curves are relative to quarks c and b (on the same curve, three dots-dashed line), s (dash-dotted), d (dashed), u (dotted) and sum of all (solid).
• Figure 2: Spectrum of charged pions after fragmentation times cross section (see Eq. (\ref{['toth']}), with $h=\pi^\pm$ and $Q^2=1\,{\rm TeV}^2$). The dotted line is the analytic fit Eq. (\ref{['fit']})which is sufficiently accurate up to $x\simeq 0.8$.
• Figure 3: The spectra of $\gamma-$rays (solid), $e^+$ (dashed), $\overline\nu_{\mu}$ (dotted), $\nu_e$ and $\nu_{\mu}$ (dash-dotted), resulting from folding Eq. (\ref{['toth']}) with the pion decay spectra.
• Figure 4: Expected $\gamma-$ray fluxes for (top to bottom) $M=0.4$, 0.6, 0.8, and 1 TeV and $\overline{J}\left(10^{-3}\right) = 500$. For comparison shown are typical $\gamma-$ray fluxes predicted for neutralinos of mass $\simeq200\,$GeV, as well as EGRET data and expected sensitivities of the future GLAST, MAGIC and HESS experiments.
• Figure 5: Value of $J=\overline{J}(10^{-3})$ required to produce $\gamma$ fluxes observable by the future GLAST, MAGIC and HESS experiments, as a function of the $B^{(1)}$ mass. For comparison we show the value of $J$ for some profiles discussed in the text.