Constraints on Light Hidden Sector Gauge Bosons from Supernova Cooling

TL;DR

This work sharpens supernova-based constraints on light hidden-sector gauge bosons that kinetically mix with photons. By systematically incorporating free-streaming emission, decay, and trapping, and by treating both proton–proton and proton–neutron bremsstrahlung channels, it yields a significantly expanded excluded region in mass–coupling space compared with prior estimates. The analysis reveals that decay and trapping shape complementary regions of viability, and it discusses the potential detectability of a diffuse background of such gauge bosons from the cosmic supernova population. Together with external constraints, these results strongly limit hidden-sector scenarios relevant to dark matter and motivate future searches for diffuse dark gauge boson backgrounds.

Abstract

We derive new bounds on hidden sector gauge bosons which could produce new energy loss mechanisms in supernovae, enlarging the excluded region in mass-coupling space by a significant factor compared to earlier estimates. Both considerations of trapping and possible decay of these particles need to be incorporated when determining such bounds, as does scattering on both neutrons and protons. For masses and couplings near the region which saturates current bounds, a significant background of such gauge bosons may also be produced due to the cumulative effects of all supernovae over cosmic history.

Figures (4)

• Figure 1: The total excluded region, adding contributions from both the $pp$ and $pn$ processes
• Figure 2: The total excluded region for MeV to GeV dark gauge boson masses is shown including the supernova bounds calculated in this work, shown in blue, along with constraints due to other sources such as beam dump experiments E774, E141, E137, contributions to the anomalous magnetic moment of the muon and the electron, $a_{\mu}$ and $a_{e}$, and BABAR bounds from upsilon $\Upsilon(3S)$ decays.
• Figure 3: Diagrams for the process $p + p \rightarrow p + p + A'$. Following Brinkmann:1988vi, these are labelled from top left to bottom left as $a, b, c, d$, and from top right to bottom right as $a', b', c', d'$.
• Figure 4: Diagrams for the process $p + n \rightarrow p + n + A'$. From top left to bottom left, the external bremsstrahlung diagrams are labelled $a$ and $c$, while from top right to bottom right, the external leg bremsstrahlung diagrams are labelled $b'$ and $c'$. The internal bremsstrahlung process is labelled $e'$.