Indirect Detection of Dirac Right-Handed Neutrino Dark Matter

TL;DR

This paper investigates indirect detection signatures of a Dirac right-handed neutrino dark matter candidate (the LZP) that can arise as a stable Kaluza-Klein state in warped GUTs with a stabilizing $Z_3$ symmetry. It analyzes three complementary channels—neutrinos from the Sun, cosmic positrons, and gamma rays near the Galactic center—across representative KK scales $M_{ m KK}$ and couplings $g_Z^{\nu'}_R$, deriving capture rates, annihilation spectra, and propagation effects. The results show that Sun neutrinos offer especially strong prospects for $M_{ m KK} \lesssim 6$ TeV, light LZPs (≈35–50 GeV) can fit HEAT-like positron data with reasonable boost factors, and gamma-ray fluxes depend sensitively on the halo profile but resemble neutralino expectations. Overall, the work demonstrates viable indirect detection pathways for Dirac RH neutrino DM in warped extra dimensions, with concrete predictions for IceCube, PAMELA/AMS-02, and gamma-ray telescopes.

Abstract

We present the signatures and prospects for the indirect detection of a Dirac right-handed neutrino dark matter candidate in neutrino telescopes, cosmic positron experiments and gamma-ray telescopes. An example of such a dark matter candidate can be found in extra-dimensional models. In some constructions, Kaluza--Klein states with the gauge quantum numbers of a right-handed neutrino can have sizable gauge interactions with Standard Model particles. For instance, in 5D warped Grand Unified Theories, it has been shown that a Kaluza--Klein right-handed neutrino may be stable and otherwise a phenomenologically viable dark matter candidate. We find that the prospects for the indirect detection of such a WIMP are encouraging, particularly for neutrino telescopes and cosmic positron experiments.

Figures (9)

• Figure 1: Predictions for $\Omega_{\hbox{\tiny LZP}} h^2$ as a function of the LZP mass for three values of the KK gauge boson mass, $M_{KK}$. In each case, the upper dashed blue line corresponds to the 'minimal' value of the $Z$-LZP coupling, $g_Z^{ \nu^{\prime}_R}$, while the lower pink curve is for a 'median' value of this coupling. In this article, we study the regions of parameter space given in the third column of Table \ref{['datasets-table']}.
• Figure 2: $\sqrt{C^{\odot} A^{\odot}} t_{\odot}$ evaluated at $\langle \sigma v \rangle \approx 3 \times 10^{-26}$ cm$^3$/s, the value of the annihilation cross section leading to the correct thermal relic density. Throughout the parameter space, the Sun consistently reaches equilibrium between the LZP capture and annihilation rates. Figure from Ref. Agashe:2004bm.
• Figure 3: The fraction of LZP annihilations to various final states. Results are shown for $m_{\rm{KK}}=4$ and 10 TeV in the left and right frames, respectively.
• Figure 4: The spectrum of neutrinos and anti-neutrinos per LZP annihilation to top quark pairs in the Sun. The effects of solar propagation have been taken into account. Results in the left and right frames correspond to LZPs with masses of 800 and 1600 GeV, respectively. Light (green) dashed, light (green) dotted, dark (blue) dashed and dark (blue) dotted lines denote $\nu_{\mu}$, $\bar{\nu_{\mu}}$, $\nu_{\tau}$ and $\bar{\nu_{\tau}}$, respectively. The solid black line is the sum of these four contributions. We have used an annihilation cross section of 3 $\times 10^{-26}$ cm$^3$/s.
• Figure 5: The number of events per year in a detector with a cubic kilometer effective area, such as IceCube. A 50 GeV muon energy threshold has been used. Solid (black) lines, dashed (blue) lines and dotted (red) lines correspond to $M_{\rm{KK}}=$4, 6 and 10 TeV, respectively. For each value of $M_{\rm{KK}}$, two lines are shown. These upper and lower lines use parameters corresponding to a 'median' and 'minimum' set of couplings (see Table \ref{['datasets-table']} for more details). Values are shown only over the mass ranges which do not overproduce the density of dark matter.