Neutrino Acceleration by Bulk Matter Motion and Explosion Mechanism of Gamma-Ray Bursts

TL;DR

This paper investigates how neutrino spectral changes caused by scattering in infalling matter can significantly enhance neutrino annihilation rates, impacting gamma-ray burst jet formation models.

Contribution

It introduces a kinetic equation approach to model neutrino acceleration and spectral change in a spherically symmetric flow, revealing a potential tenfold increase in annihilation rates.

Findings

Neutrinos can be accelerated to nonthermal spectra through scattering.

Accelerated neutrinos can boost annihilation rates by approximately ten times.

Spectral changes depend on the optical depth of the infalling material.

Abstract

The neutrino annihilation is one of the most promising candidates for the jet production process of gamma-ray bursts. Although neutrino interaction rates depend strongly on the neutrino spectrum, the estimations of annihilation rate have been done with an assumption of the neutrino thermal spectrum based on the presence of the neutrinospheres, in which neutrinos and matter couple strongly. We consider the spectral change of neutrinos caused by the scattering by infalling materials and amplification of the annihilation rate. We solve the kinetic equation of neutrinos in spherically symmetric background flow and find that neutrinos are successfully accelerated and partly form nonthermal spectrum. We find that the accelerated neutrinos can significantly enhance the annihilation rate by a factor of $\sim 10$, depending on the injection optical depth.