Muonic Boson Limits: Supernova Redux

TL;DR

This paper derives supernova bounds on muon-philic bosons, considering scalar and pseudoscalar particles with photon couplings, and analyzes their implications for astrophysics and the muon magnetic moment anomaly.

Contribution

It introduces systematic constraints on muonic bosons, including scalars, using supernova models and photon coupling interactions, extending previous bounds to new particle types.

Findings

SN1987A gamma-ray bounds limit boson couplings for masses above 100 keV.

Fast decay of bosons into photons dumps energy into the star, reducing explosion energy.

Muonic scalars can potentially explain the muon magnetic moment anomaly.

Abstract

We derive supernova (SN) bounds on muon-philic bosons, taking advantage of the recent emergence of muonic SN models. Our main innovations are to consider scalars $\phi$ in addition to pseudoscalars $a$ and to include systematically the generic two-photon coupling $G_{\gamma\gamma}$ implied by a muon triangle loop. This interaction allows for Primakoff scattering and radiative boson decays. The globular-cluster bound $G_{\gamma\gamma}<0.67\times10^{-10}~{\rm GeV}^{-1}$ derived for axion-like particles carries over to the muonic Yukawa couplings as $g_a<3.1\times10^{-9}$ and $g_\phi< 4.6\times10^{-9}$ for $m_{a,\phi}\lesssim 100$ keV, so SN arguments become interesting mainly for larger masses. If bosons escape freely from the SN core the main constraints originate from SN1987A $\gamma$ rays and the diffuse cosmic $\gamma$-ray background. The latter allows at most $10^{-4}$ of a typical total SN energy of $E_{\rm SN}\simeq3\times10^{53}$erg to show up as $\gamma$ rays, for $m_{a,\phi}\gtrsim 100$keV implying $g_a \lesssim 0.9\times10^{-10}$ and $g_\phi \lesssim 0.4\times10^{-10}$. In the trapping regime the bosons emerge as quasi-thermal radiation from a region near the neutrino sphere and match $L_\nu$ for $g_{a,\phi}\simeq 10^{-4}$. However, the $2\gamma$ decay is so fast that all the energy is dumped into the surrounding progenitor-star matter, whereas at most $10^{-2}E_{\rm SN}$ may show up in the explosion. To suppress boson emission below this level we need yet larger couplings, $g_{a}\gtrsim 2\times10^{-3}$ and $g_{\phi}\gtrsim 4\times10^{-3}$. Muonic scalars can explain the muon magnetic-moment anomaly for $g_{\phi}\simeq 0.4\times10^{-3}$, a value hard to reconcile with SN physics despite the uncertainty of the explosion-energy bound. For generic axion-like particles, this argument covers the "cosmological triangle" in the $G_{a\gamma\gamma}$--$m_a$ parameter space.