Multi-GeV neutrinos from internal dissipation in gamma-ray burst fireballs

Subphotospheric internal shocks and transverse differences of the bulk Lorentz factor in relativistic fireball models of gamma-ray bursts (GRBs) lead to neutron diffusion relative to protons, resulting in inelastic nuclear collisions. This results in significant fluxes of ν_μ(ν̄_μ) of ∼3 GeV and ν_e(ν̄_e) of ∼2 GeV, scaling with the flow Lorentz factor η < η_π ∼ 400. This extends significantly the parameter space for which neutrinos from inelastic collision are expected, which in the absence of the above effects requires values in excess of η_π. A model with sideways diffusion of neutrons from a slower wind into a fast jet can lead to production of ν_μ(ν̄_μ) and ν_e(ν̄_e) in the range 2-25 GeV or higher, depending on the value of η. The emission from either of these mechanisms from GRBs at redshifts z ∼ 1 may be detectable in suitably densely spaced detectors.