5–10 GeV Neutrinos from Gamma-Ray Burst Fireballs

Abstract

A gamma-ray burst fireball is likely to contain an admixture of neutrons. Inelastic collisions between differentially streaming protons and neutrons in the fireball produce ${\nu }_{\mu }$ $\left({\overline{\nu }}_{\mu }\right)$ of $\sim 10\mathrm{GeV}$ as well as ${\nu }_e$ $\left({\overline{\nu }}_e\right)$ of $\sim 5\mathrm{GeV}$, which could produce $\sim 7\mathrm{events}/\mathrm{year}$ in ${\mathrm{km}}^3$ detectors, if the neutron abundance is comparable to that of protons. Photons of $\sim 10\mathrm{GeV}$ from ${\pi }^0$ decay and $\sim 100\mathrm{MeV}$ ${\overline{\nu }}_e$ from neutron decay are also produced, but will be difficult to detect. Photons with energies $\lesssim 1\mathrm{MeV}$ from shocks following neutron decay produce a characteristic signal which may be distinguishable from the proton-related MeV photons.