Multi-GeV Neutrinos from Internal Dissipation in GRB Fireballs

Sub-photospheric internal shocks and transverse differences of the bulk Lorentz factor in relativistic fireball models of GRB lead to neutron diffusion relative to protons, resulting in inelastic nuclear collisions. This results in significant fluxes of νμ(ν̄μ) of ∼ 3 GeV and νe(ν̄e) of ∼ 2 GeV, scaling with the flow Lorentz factor η < ηπ ∼ 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 ηπ. A model with sideways diffusion of neutrons from a slower wind into a fast jet can lead to production of νμ(ν̄μ) and νe(ν̄e) in the 2-25 GeV or higher range, depending on the value of η. The emission from either of these mechanisms from GRB at redshifts z ∼ 1 may be detectable in suitably densely spaced detectors. Subject headings: Gamma-rays: Bursts Neutrinos Cosmology: Miscellaneous