Neutrino Spectral Pinching in 3D Core-Collapse Supernovae: Late-Time Convergence, Failed-Explosion Signatures, and Viewing-Angle Dispersion

TL;DR

This paper systematically analyzes neutrino spectral pinching in 3D supernova simulations, revealing convergence, signatures of failed explosions, and viewing-angle effects, with implications for neutrino detection and supernova physics.

Contribution

It provides the first detailed 3D characterization of neutrino spectral pinching and its evolution across diverse supernova models, including late-time convergence and asymmetry effects.

Findings

Nu-bar_e pinching floor is 1.92 +/- 0.10, below 1D predictions due to 3D convection.

BH-forming models show anti-pinching before collapse with a deficit of ~0.65.

Viewing-angle spread dominates spectral-inversion uncertainty, affecting detection interpretations.

Abstract

We present a systematic survey of the neutrino spectral pinching parameter alpha_p(t, M, n-hat) across the Princeton Fornax ensemble of 3D core-collapse supernova simulations. We analyze 25 simulations spanning progenitor masses 8.1-100 M_sun with durations up to 8.47 s post-bounce, computed with the Fornax code and the SFHo equation of state. The pinching parameter alpha_p = (2^2 - E_rms^2)/(E_rms^2 - ^2) is derived from 12-bin spectral moments on a 128x256 sky grid for three neutrino species, enabling time- and angle-resolved spectral characterization. Four results emerge. (1) The nu-bar_e pinching floor is alpha_p = 1.92 +/- 0.10 (N=13 long-running models), lying 0.2-0.4 below 1D predictions due to 3D PNS convection. (2) Both BH-forming models (12.25, 14 M_sun) show anti-pinching (alpha_p < 0.9) before collapse, with deficit Delta alpha_p ~ 0.65 visible from t = 0.5 s. (3) Two of six long-running models exhibit a hierarchy reversal ( > ) after t = 5 s; leptonic flavors carry (40 +/- 3)% of radiated energy. (4) The LESA dipole is suppressed by >3x in BH-forming models; viewing-angle spread Delta alpha_p(68%) ~ 0.8-1.5 dominates spectral-inversion uncertainty. Mollweide sky maps reveal coherent angular structures with alpha_p anticorrelated with luminosity and correlated with mean energy. Detection rates at Hyper-Kamiokande, DUNE, JUNO, and IceCube yield 8-12% NMO/IMO discrimination during Kelvin-Helmholtz cooling. The late-time nu-bar_e pinching floor represents the first 3D characterization of spectral convergence during Kelvin-Helmholtz cooling.