Muonic boson limits: Supernova redux

Low-Energy Supernovae Severely Constrain Radiative Particle Decays

“…A precise evaluation in a SN core is difficult because electrons are relativistic and degenerate, however implying that their contribution both as scattering targets and for screening is small. We follow our earlier discussion [7] and neglect electrons, so for screening we use the Debye-Hückel scale of the quasi-static ions…”

“…While in a SN core, the charged particles are typically protons, in some regions small nuclear clusters dominate instead. Following our earlier discussion [7], we use Ŷ = 1 − Y n for estimating the Primakoff production and absorption rate in a given SN model. Photons in the medium suffer nontrivial dispersion that is dominated by the relativistic electron plasma frequency ω 2 p = (4α/3π)(µ 2 e + π 2 T 2 /3), where µ e is the electron chemical potential.…”

“…The temperature scale of a SN core is 30 MeV, resulting in an energy scale of 100 MeV for the emitted particles and their decay products. The decay photons from all past SNe contribute excessively to the cosmic diffuse γ-ray background unless the energy loss of an average SN in this form is below 0.015-0.03 B, using (0.5-1) × 10 7 Mpc −3 for the comoving cosmic density of all past core collapses [3][4][5][6][7]. This small energy loss is to be compared with a typical neutron-star binding energy of 200-400 B, depending on its mass and the nuclear equation of state.…”

“…This idea was first advanced by Falk and Schramm a decade before SN 1987A [12], recently rediscovered [13], and applied to muon-philic bosons [7] and generic e + e − decays [14]. Moreover, it was speculated that such effects could power SN explosions [15][16][17] or gamma-ray bursts [18,19].…”

“…2. We also indicate the constraint from the absence of excess γ-ray counts in conjunction with the SN 1987A neutrino signal [11] (solid green), the bounds from beam dump experiments [59] (purple contour), and the free streaming limit of the neutrino cooling argument for SN1987A [7] (solid blue).…”