Assessing the Relative Importance of Neutrino Matter Interaction Channels in Post-Merger Remnant of Binary Neutron Stars

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Auteurs principaux: Rath, Samantha, Foucart, Francois, Kidder, Lawrence E., Pfeiffer, Harald P., Scheel, Mark A.
Format: Preprint
Publié: 2026
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author Rath, Samantha
Foucart, Francois
Kidder, Lawrence E.
Pfeiffer, Harald P.
Scheel, Mark A.
author_facet Rath, Samantha
Foucart, Francois
Kidder, Lawrence E.
Pfeiffer, Harald P.
Scheel, Mark A.
contents Neutron star mergers are amongst the most promising sources for the joint detection of gravitational waves and electromagnetic signals. They are also potential sites for the production of r-process elements and probes of the equation of state of matter above nuclear saturation density. Neutrino-matter interactions during and after merger strongly influence the thermodynamic evolution and composition of the remnant and its outflows, thereby affecting kilonova emission and nucleosynthesis yields. However, existing merger simulations remain limited by significant approximations in the treatment of neutrino transport and interaction rates. In this work, we assess the thermodynamic conditions under which neutrinos decouple from matter and show the effect of charged-current absorption, quasi-elastic scattering on nucleons and nuclei, pair-production processes, and inelastic neutrino-electron scattering for electron neutrinos, electron antineutrinos, and heavy-lepton neutrinos in the different thermodynamical conditions sampled by a simulation using an energy-dependent Monte Carlo neutrino transport. We first estimate opacities in the post-merger remnant assuming neutrinos in equilibria with the fluid, and find results consistent with previous studies performed on simulations using a gray two-moment scheme. We note the very distinct regions in which nucleon-nucleon Bremmstrahlung and electron-positron annihilation are active (high and low density regions, respectively). We then evaluate opacities using the actual distribution function of neutrinos within a Monte Carlo simulation. We show greatly increased pair annihilation rates in cold, low-density regions, especially for heavy-lepton neutrinos. We also show that inelastic scattering on electrons, which has not been included in merger simulations so far, makes important contributions to the thermalization of heavy-lepton neutrinos.
format Preprint
id arxiv_https___arxiv_org_abs_2605_29187
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Assessing the Relative Importance of Neutrino Matter Interaction Channels in Post-Merger Remnant of Binary Neutron Stars
Rath, Samantha
Foucart, Francois
Kidder, Lawrence E.
Pfeiffer, Harald P.
Scheel, Mark A.
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
Neutron star mergers are amongst the most promising sources for the joint detection of gravitational waves and electromagnetic signals. They are also potential sites for the production of r-process elements and probes of the equation of state of matter above nuclear saturation density. Neutrino-matter interactions during and after merger strongly influence the thermodynamic evolution and composition of the remnant and its outflows, thereby affecting kilonova emission and nucleosynthesis yields. However, existing merger simulations remain limited by significant approximations in the treatment of neutrino transport and interaction rates. In this work, we assess the thermodynamic conditions under which neutrinos decouple from matter and show the effect of charged-current absorption, quasi-elastic scattering on nucleons and nuclei, pair-production processes, and inelastic neutrino-electron scattering for electron neutrinos, electron antineutrinos, and heavy-lepton neutrinos in the different thermodynamical conditions sampled by a simulation using an energy-dependent Monte Carlo neutrino transport. We first estimate opacities in the post-merger remnant assuming neutrinos in equilibria with the fluid, and find results consistent with previous studies performed on simulations using a gray two-moment scheme. We note the very distinct regions in which nucleon-nucleon Bremmstrahlung and electron-positron annihilation are active (high and low density regions, respectively). We then evaluate opacities using the actual distribution function of neutrinos within a Monte Carlo simulation. We show greatly increased pair annihilation rates in cold, low-density regions, especially for heavy-lepton neutrinos. We also show that inelastic scattering on electrons, which has not been included in merger simulations so far, makes important contributions to the thermalization of heavy-lepton neutrinos.
title Assessing the Relative Importance of Neutrino Matter Interaction Channels in Post-Merger Remnant of Binary Neutron Stars
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2605.29187