Magnetic Field and Flavor Effects on the Gamma-Ray Burst Neutrino Flux

TL;DR

This paper reexamines the predicted muon neutrino flux from gamma-ray bursts, incorporating magnetic field effects and flavor mixing, revealing significant modifications to the expected flux shape and normalization, impacting neutrino telescope search strategies.

Contribution

It introduces a comprehensive reanalysis of the GRB neutrino flux by including additional production modes and physical effects, providing more accurate flux predictions.

Findings

Flux shape is significantly altered by magnetic and flavor effects.

Normalization of the flux changes by a factor of three to four.

Current constraints on GRB neutrino flux may be stronger than previously thought.

Abstract

We reanalyze the prompt muon neutrino flux from gamma-ray bursts (GRBs), at the example of the often used reference Waxman-Bahcall GRB flux, in terms of the particle physics involved. We first reproduce this reference flux treating synchrotron energy losses of the secondary pions explicitly. Then we include additional neutrino production modes, the neutrinos from muon decays, the magnetic field effects on all secondary species, and flavor mixing with the current parameter uncertainties. We demonstrate that the combination of these effects modifies the shape of the original Waxman-Bahcall GRB flux significantly, and changes the normalization by a factor of three to four. As a consequence, the gamma-ray burst search strategy of neutrino telescopes may be based on the wrong flux shape, and the constraints derived for the GRB neutrino flux, such as the baryonic loading, may in fact be already much stronger than anticipated.