IceCube constraints on the Fermi Bubbles

We analyze the IceCube four-year neutrino data in search of a signal from the Fermi bubbles. No signal is found from the bubbles or from their dense shell, even when taking into account the softer background. This imposes a conservative $xi_i<8%$ upper limit on the cosmic-ray ion (CRI) acceleration efficiency, and an $etaequiv xi_e/xi_i gtrsim0.006$ lower limit on the electron-to-ion ratio of acceleration efficiencies (at the $2sigma$ confidence level). For typical $xi_i$, a signal should surface once the number of IceCube neutrinos increases by $sim$an order of magnitude, unless there is a $<$PeV cutoff on the CRI spectrum.