Nambu-Goldstone Dark Matter and Cosmic Ray Electron and Positron Excess

We propose a model of dark matter identified with a pseudo-Nambu-Goldstone boson in the dynamical supersymmetry breaking sector in a gauge mediation scenario. The dark matter particles annihilate via a below-threshold narrow resonance into a pair of R-axions each of which subsequently decays into a pair of light leptons. The Breit-Wigner enhancement explains the excess electron and positron fluxes reported in the recent cosmic ray experiments PAMELA, ATIC and PPB-BETS without postulating an overdensity in halo, and the limit on anti-proton flux from PAMELA is naturally evaded.

💡 Research Summary

The authors present a novel dark‑matter (DM) framework in which the DM particle is identified with a pseudo‑Nambu‑Goldstone boson (pNG) arising from a dynamical supersymmetry‑breaking (DSB) sector that is coupled to the visible sector through gauge mediation. In this construction the DSB sector possesses a global symmetry that is spontaneously broken, giving rise to a genuine Goldstone mode. Supersymmetry breaking then endows this mode with a small mass, turning it into a pNG boson χ with a mass in the TeV range (≈1–2 TeV).

A second light scalar, the R‑axion, appears as the pseudo‑Goldstone boson associated with the explicit breaking of the R‑symmetry of the DSB sector. Its mass is tuned to lie just below the χχ̄ annihilation threshold (m_R ≲ 2 m_χ) and its width is extremely narrow (Γ_R/m_R ≈ 10⁻⁴–10⁻³). When two χ particles annihilate, the process is dominated by an s‑channel exchange of this R‑axion. Because the resonance is narrow and sits slightly below the kinematic threshold, the annihilation cross‑section receives a Breit‑Wigner (BW) enhancement:

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