Interactions with neutrons and protons play a crucial role for the neutrino opacity of matter in the supernova core .
Their current implementation in many simulation codes , however , is rather schematic and ignores not only modifications for the correlated nuclear medium of the nascent neutron star , but also free-space corrections from nucleon recoil , weak magnetism or strange quarks , which can easily add up to changes of several 10 % for neutrino energies in the spectral peak .
In the Garching supernova simulations with the Prometheus-Vertex code , such sophistications have been included for a long time except for the strange-quark contributions to the nucleon spin , which affect neutral-current neutrino scattering .
We demonstrate on the basis of a 20 M _ { \odot } progenitor star that a moderate strangeness-dependent contribution of g _ { \mathrm { a } } ^ { \mathrm { s } } = -0.2 to the axial-vector coupling constant g _ { \mathrm { a } } \approx 1.26 can turn an unsuccessful three-dimensional ( 3D ) model into a successful explosion .
Such a modification is in the direction of current experimental results and reduces the neutral-current scattering opacity of neutrons , which dominate in the medium around and above the neutrinosphere .
This leads to increased luminosities and mean energies of all neutrino species and strengthens the neutrino-energy deposition in the heating layer .
Higher nonradial kinetic energy in the gain layer signals enhanced buoyancy activity that enables the onset of the explosion at \sim 300 ms after bounce , in contrast to the model with vanishing strangeness contributions to neutrino-nucleon scattering .
Our results demonstrate the close proximity to explosion of the previously published , unsuccessful 3D models of the Garching group .