Revisiting Supernova 1987A Constraints on Dark Photons (1611.03864v4)

Abstract: We revisit constraints on dark photons with masses below ~ 100 MeV from the observations of Supernova 1987A. If dark photons are produced in sufficient quantity, they reduce the amount of energy emitted in the form of neutrinos, in conflict with observations. For the first time, we include the effects of finite temperature and density on the kinetic-mixing parameter, epsilon, in this environment. This causes the constraints on epsilon to weaken with the dark-photon mass below ~ 15 MeV. For large-enough values of epsilon, it is well known that dark photons can be reabsorbed within the supernova. Since the rates of reabsorption processes decrease as the dark-photon energy increases, we point out that dark photons with energies above the Wien peak can escape without scattering, contributing more to energy loss than is possible assuming a blackbody spectrum. Furthermore, we estimate the systematic uncertainties on the cooling bounds by deriving constraints assuming one analytic and four different simulated temperature and density profiles of the proto-neutron star. Finally, we estimate also the systematic uncertainty on the bound by varying the distance across which dark photons must propagate from their point of production to be able to affect the star. This work clarifies the bounds from SN1987A on the dark-photon parameter space.

• The paper introduces finite temperature and density corrections to the kinetic mixing parameter, weakening constraints for dark photon masses below 15 MeV.
• It employs one analytic model alongside four simulated proto-neutron star profiles to rigorously assess systematic uncertainties in dark photon cooling bounds.
• The study reveals that high-energy dark photons can escape via reduced reabsorption, emphasizing non-thermal emission effects and motivating further dark sector research.

Revisiting Supernova 1987A Constraints on Dark Photons

This paper presents a comprehensive re-evaluation of the constraints imposed on dark photons from observations of Supernova 1987A (SN1987A), with a particular focus on masses below approximately 100 MeV. The motivation for this paper lies in the hypothesis that if dark photons were produced in significant quantities during the supernova, they could have reduced the energy released in neutrinos, presenting a conflict with empirical observations. A novel aspect of this work is the inclusion of finite temperature and density effects on the kinetic mixing parameter, $\epsilon$, within the supernova environment—a factor previously neglected in similar studies.

The authors observe that these environmental conditions result in a weakening of constraints on $\epsilon$ for dark-photon masses lower than approximately 15 MeV. An interesting feature of the analysis is the consideration of reabsorption of dark photons within the supernova at large values of $\epsilon$. The probability of this reabsorption drops as the energy of the dark photons rises, enabling high-energy dark photons exceeding the Wien peak to escape the supernova without scattering. The implication is that they contribute more significantly to energy loss than would be anticipated by a simple blackbody spectrum assumption.

A rigorous evaluation of systematic uncertainty is a central component of this paper. The authors achieve this by deriving constraints based on one analytic model and four different simulated temperature and density profiles reflective of the proto-neutron star's environment. These simulations help to estimate the uncertainty on the cooling bounds due to variations in distance over which dark photons must propagate to influence the supernova observations.

From a theoretical perspective, this work refines the understanding of supernova constraints on dark-photon parameter space. For small mixing angles, the resonance condition draws a direct correlation between the plasma mass of the photon and the dark photon mass, influencing the effective kinetic mixing. The energy spectra and implications of the systematic change in the resonance peak are carefully quantified. The paper suggests that for small masses and low mixing angles, the resonance-induced production remains significant, weakening for larger mixing angles due to increased reabsorption.

On the practical implications of these findings, the paper alerts to the importance of considering finite-temperature effects and the non-thermal nature of the dark-photon emission spectrum in future astrophysical studies. The results not only offer revised constraints but also serve to caution against simplistic applications of thermal spectra assumptions in similar environmental settings.

Future research could expand upon this work by exploring the interplay between dark photons and other potential low-mass dark-sector particles in stellar environments, potentially illuminating new pathways for identifying dark-matter candidates. This paper sets a foundation for such studies, underscoring the complexity and necessity of accounting for environmental factors in theoretical astrophysics.

In summary, the insights and methodological innovations presented in this paper afford a refined understanding of the constraints on dark photons, indirectly contributing valuable data to the wider discourse on dark sector physics and their manifestations in cosmic events like supernovae.