Relativistic outflows with neutrons inevitably lead to inelastic collisions, and resulting subphotospheric $\gamma$ rays may explain prompt emission of $\gamma$-ray bursts. In this model, hadronuclear, quasithermal neutrinos in the 10–100 GeV range should be generated, and they may even have a high-energy tail by neutron-proton-converter or shock acceleration mechanisms. We demonstrate the importance of dedicated searches with $\mathrm{\text{DeepCore}}+\mathrm{\text{IceCube}}$, though such analyses have not been performed. Successful detections enable us to discriminate among prompt emission mechanisms, probe the jet composition, and see roles of relativistic neutrons as well as effects of cosmic-ray acceleration.

• Received 17 January 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.131102