Ultrahigh Energy Neutrinos from Gamma Ray Bursts

Protons accelerated to high energies in the relativistic shocks that generate gamma ray bursts photoproduce pions, and then neutrinos in situ. I show that ultrahigh energy neutrinos ( $>{10}^{19}\mathrm{eV}$) are produced during the burst and the afterglow. A larger flux, also from bursts, is generated via photoproduction off cosmic microwave background photons in flight but is not correlated with currently observable bursts, appearing as a bright background. Adiabatic and synchrotron losses from protons, pions, and muons are negligible. Temporal and directional coincidences with bursts detected by satellites can separate correlated neutrinos from the background.