Ultrahigh energy neutrinos from population III stars: Concept and constraints

In this paper we reconsider the model of neutrino production during the "bright phase,'' first suggested in 1977, in the light of modern understanding of both the role of Pop III stars and of acceleration of particles in supernova shocks. We concentrate on the production of cosmogenic ultrahigh energy neutrinos in supernova (SN) explosions that accompany the death of massive Population III stars. Protons are assumed to be accelerated at such SN shocks and produce neutrinos in collisions with CMB photons. In the calculations we deliberately use simplified assumptions which make the physical results transparent. Pop III stars, either directly or through their SN explosions, are assumed to be responsible for the reionization of the universe as observed by WMAP. Since the evolution of massive Pop III stars occurs on time scales much shorter than the Hubble time H-1, we consider the burst of UHE proton production to occur at fixed redshift (z(b) = 10 and z(b) = 20), though more realistic models can easily be built. We discuss in some detail the problems involved in the formation of collisionless shocks in the early universe as well as the acceleration of charged particles in a medium that has potentially very low preexisting magnetization, if any at all. The composition of the accelerated particles in Pop III stars explosions is expected to be proton dominated, based upon the predictions of BBN and the Hydrogen-enhanced stellar-wind from primary Pop III stars. A simple calculation is presented to illustrate the fact that the diffuse neutrino flux from the bright phase burst is concentrated in a relatively narrow energy interval, centered at E-nu(c) = 7.5 x 10(15)(20/z(b))(2) eV. The nu(mu) flux may be detectable by IceCube without violating the cascade upper limit and without exceeding the expected energetics of SNe associated with Pop III stars. A possible signature of the neutrino production from Pop III stars may be the detection of resonant neutrino events ((nu) over bar (e) + e(-) -> W- -> hadrons) at energy E-0 = 6.3 x 10(15) eV. For the burst at z(b) = 20 and ((nu) over bar (e)-flux at the cascade upper limit, the number of resonant events in IceCube may be as high as 10 events in 5 years of observations. These events have equal energies, E = 6.3 x 10(15) eV, in the form of e-m cascades. Taking into account the large uncertainties in the existing predictions of cosmogenic neutrino fluxes at E > 10(15) eV, we argue that UHE neutrinos from the first stars might become one of the most reliable hopes for UHE neutrino astronomy.