Δ(1232) isobars and neutrino opacities in hot dense matter
Abstract
We calculated the diffusion mean free paths of electron neutrinos and antineutrinos in hot, neutrino-trapped matter containing Δ(1232) isobars, as found in proto-neutron stars and neutron star merger remnants. We included charged-current absorption with the NΔ weak vertex of weak pion production, neutral-current scattering on all baryons and three-body antineutrino absorption on electron--baryon pairs, with relativistic mean-field kinematics. The reaction ν̅e+e-+n→Δ- dominates the antineutrino opacity whenever the neutron and electron chemical potentials exceed the in-medium Δ- rest energy, even where the Δ population is negligible. At two to four times saturation density, where the reaction is open, it shortens the antineutrino mean free path from \nubarLamNucMin--\nubarLamNucMax~m to \nubarLamDMin--\nubarLamDMax~cm. Because antineutrinos are scarce at high lepton fraction, this changes lepton-number diffusion only at low lepton fraction, by up to \DtwoRedHi\% at these densities and by a factor of \DtwoRedLow\ at 1.5 times saturation density. For electron neutrinos, absorption on the Δ- and, at low lepton fraction, the opening of nucleonic absorption shorten the mean free path by factors of up to \nuRatioYLthreeMax\ at lepton fraction 0.3 and up to about \nuRatioYLoneMax\ at lepton fraction 0.1. We also showed that, for a given axial coupling, the spin of the Δ reduces its Gamow--Teller strength per particle from 3 to 5/3.
Related
- Collective flavor conversion in dense neutrino plasmas
- Solar Neutrino Constraints on Inelastic Dark Matter Scattering in Light of Recent LUX-ZEPLIN Observations
- High resolution Lyman-α forest constraints on dark matter-neutrino scattering
- Searching for Dense Perturbers in Cold Dark Matter Simulations
- Evidence for a Continuous Hadron--Quark Transition in Cold Dense Matter
BibTeX
@misc{mitra2026δ1232,
title = {{$Δ(1232)$ isobars and neutrino opacities in hot dense matter}},
author = {Subha Mitra and Bharat Kumar},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.35156},
eprint = {2610.35156},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.35156},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Δ(1232) isobars and neutrino opacities in hot dense matter
AU - Subha Mitra
AU - Bharat Kumar
PY - 2026
DA - 2026/10/26
PB - arXiv
DO - 10.48550/arxiv.2610.35156
UR - https://arxiv.org/abs/2610.35156
AB - We calculated the diffusion mean free paths of electron neutrinos and antineutrinos in hot, neutrino-trapped matter containing Δ(1232) isobars, as found in proto-neutron stars and neutron star merger remnants. We included charged-current absorption with the NΔ weak vertex of weak pion production, neutral-current scattering on all baryons and three-body antineutrino absorption on electron--baryon pairs, with relativistic mean-field kinematics. The reaction ν̅_e+e^-+n→Δ^- dominates the antineutrino opacity whenever the neutron and electron chemical potentials exceed the in-medium Δ^- rest energy, even where the Δ population is negligible. At two to four times saturation density, where the reaction is open, it shortens the antineutrino mean free path from \nubarLamNucMin--\nubarLamNucMax~m to \nubarLamDMin--\nubarLamDMax~cm. Because antineutrinos are scarce at high lepton fraction, this changes lepton-number diffusion only at low lepton fraction, by up to \DtwoRedHi\% at these densities and by a factor of \DtwoRedLow\ at 1.5 times saturation density. For electron neutrinos, absorption on the Δ^- and, at low lepton fraction, the opening of nucleonic absorption shorten the mean free path by factors of up to \nuRatioYLthreeMax\ at lepton fraction 0.3 and up to about \nuRatioYLoneMax\ at lepton fraction 0.1. We also showed that, for a given axial coupling, the spin of the Δ reduces its Gamow--Teller strength per particle from 3 to 5/3.
ER -