Cosmic Signals from the Hidden Sector

TL;DR

Cosmic Signals from the Hidden Sector investigates a SUSY-breaking hidden sector at $\Lambda \sim 10-100$ TeV in which DM is a heavy, quasi-stable composite state and light axion-like particles arise from broken global symmetries. DM decays via dimension-six operators into axions that subsequently decay to leptons, naturally explaining the PAMELA, FERMI, and H.E.S.S. cosmic-ray observations while predicting distinctive diffuse gamma-ray signatures. The authors present a concrete SUSY QCD-inspired illustration in which the correct thermal relic abundance is achieved and decays proceed through an axion portal, and they discuss collider prospects for detecting the axion-like states and possible Higgs decays to aa. Overall, the work links hidden-sector strong dynamics to observable astrophysical signals and collider phenomenology, highlighting the potential of future gamma-ray measurements and LHC searches to probe the structure of SUSY breaking and the associated dark sector.

Abstract

Cosmologically long-lived, composite states arise as natural dark matter candidates in theories with a strongly interacting hidden sector at a scale of 10 - 100 TeV. Light axion-like states, with masses in the 1 MeV - 10 GeV range, are also generic, and can decay via Higgs couplings to light standard model particles. Such a scenario is well motivated in the context of very low energy supersymmetry breaking, where ubiquitous cosmological problems associated with the gravitino are avoided. We investigate the astrophysical and collider signatures of this scenario, assuming that dark matter decays into the axion-like states via dimension six operators, and we present an illustrative model exhibiting these features. We conclude that the recent data from PAMELA, FERMI, and H.E.S.S. points to this setup as a compelling paradigm for dark matter. This has important implications for future diffuse gamma ray measurements and collider searches.

Figures (7)

• Figure 1: A schematic depiction of the setup.
• Figure 2: A schematic picture for the constraints on the $m_a$-$f_a$ plane, with the shaded region corresponding to the excluded region. Note that the actual limits on $f_a$ have $O(1)$ uncertainties, as explained in the text. The dominant $a$ decay mode for a given value of $m_a$ is also depicted.
• Figure 3: Cascade decays of dark matter $\phi$ through an axion-like state $a$. Here, $\phi'$ is an unstable state in the supersymmetry breaking sector, and $\ell^\pm$ ($\ell = e,\mu,\tau$) are standard model leptons.
• Figure 4: Regions of best fit (at $68\%$ C.L.) to the PAMELA and FERMI data for dark matter mass $m_{\rm DM}$ and lifetime $\tau_{\rm DM}$, in the case of direct (solid), $1$-step (dashed), and $2$-step (dotted) decays into $e^+e^-$, $\mu^+\mu^-$, and $\tau^+\tau^-$. The best fit values of $m_{\rm DM}$ and $\tau_{\rm DM}$ are indicated by the crosses, and are displayed inset in units of TeV and $10^{26}~{\rm sec}$, respectively. Direct decays into $e^+e^-$ does not give a good fit. The case of $\pi^+\pi^-\pi^0$ is similar to that of $\tau^+\tau^-$.
• Figure 5: The predicted $e^\pm$ fluxes compared to the PAMELA and FERMI data for $1$-step cascade decays into $e^+e^-$, $\mu^+\mu^-$, and $\tau^+\tau^-$. In each case, the mass and lifetime of dark matter are chosen at the best fit point indicated in Figure \ref{['fig:best-fit']}, with the background (dotted) and FERMI energy-normalization marginalized as described in the text. We overlay the H.E.S.S. data with energy rescaled in the range $\pm 15\%$ to best match the theory. Note that due to considerable uncertainty in the background fluxes at H.E.S.S. energies, direct comparison of predicted fluxes with the H.E.S.S. data may be misleading.