Constructing angular distributions of neutrinos in core-collapse supernovae from zeroth and first moments calibrated by full Boltzmann neutrino transport

Hiroki Nagakura and Lucas Johns
Phys. Rev. D 103, 123025 – Published 28 June 2021

Abstract

Two-moment neutrino transport methods have been widely used for developing theoretical models of core-collapse supernovae (CCSN), since they substantially reduce the computational burden inherent in the multidimensional neutrino-radiation hydrodynamical simulations. The approximation, however, comes at a price; the detailed structure of angular distribution of neutrinos is sacrificed, that is the main drawback of this approach. In this paper, we develop a novel method by which to construct angular distributions of neutrinos from the zeroth and first angular moments. In our method, the angular distribution is expressed with two quadratic functions of the neutrino angle in a piecewise fashion. We determine the best parameters in the fitting function by comparing to the neutrino data in a spherically symmetric CCSN model with full Boltzmann neutrino transport. We demonstrate the capability of our method by using our recent 2D CCSN model. We find that the essential features of the angular distributions can be well reconstructed, whereas the angular distributions of incoming neutrinos tend to have large errors that increase with flux factor (κ). This issue originates from the insensitiveness of incoming neutrinos to κ, that is an intrinsic limitation in moment methods. Based on the results of the demonstration, we assess the reliability of electron- neutrinos lepton number (ELN)-crossing searches with the two-moment neutrino transport. This analysis is complementary to our [L. Johns and H. Nagakura arXiv:2104.04106] that scrutinizes the limitation of crossing searches with a few moments. We find that the systematic errors of angular distributions for incoming neutrinos lead to misjudgements of the crossing at κ0.5. This casts doubt on the results of ELN-crossing searches based on two-moment methods in some previous studies.

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  • Received 15 April 2021
  • Accepted 21 May 2021

DOI:https://doi.org/10.1103/PhysRevD.103.123025

© 2021 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
Gravitation, Cosmology & Astrophysics

Authors & Affiliations

Hiroki Nagakura1,* and Lucas Johns2,†

  • 1Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, New Jersey 08544, USA
  • 2Department of Physics, University of California, Berkeley, California 94720, USA

  • *hirokin@astro.princeton.edu
  • ljohns@berkeley.edu

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Issue

Vol. 103, Iss. 12 — 15 June 2021

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