Abstract
We consider the constraints from Supernova 1987A on particles with small couplings to the Standard Model. We discuss a model with a fermion coupled to a dark photon, with various mass relations in the dark sector; millicharged particles; dark-sector fermions with inelastic transitions; the hadronic QCD axion; and an axion-like particle that couples to Standard Model fermions with couplings proportional to their mass. In the fermion cases, we develop a new diagnostic for assessing when such a particle is trapped at large mixing angles. Our bounds for a fermion coupled to a dark photon constrain small couplings and masses ≲ 200 MeV, and do not decouple for low fermion masses. They exclude parameter space that is otherwise unconstrained by existing accelerator-based and direct-detection searches. In addition, our bounds are complementary to proposed laboratory searches for sub-GeV dark matter, and do not constrain several benchmark-model targets in parameter space for which the dark matter obtains the correct relic abundance from interactions with the Standard Model. For a millicharged particle, we exclude charges between 10−9–few×10−6 in units of the electron charge, also for masses ≲ 200 MeV; this excludes parameter space to higher millicharges and masses than previous bounds. For the QCD axion and an axion-like particle, we apply several updated nuclear physics calculations and include the energy dependence of the optical depth to accurately account for energy loss at large couplings. These corrections allow us to rule out a hadronic axion of mass between 0.1 and a few hundred eV, or equivalently to put a bound on the scale of Peccei-Quinn symmetry breaking between a few×104 and 108 GeV, closing the hadronic axion window. For an axion-like particle, our bounds disfavor decay constants between a few×105 GeV up to a few×108 GeV, for a mass ≲ 200 MeV. In all cases, our bounds differ from previous work by more than an order of magnitude across the entire parameter space. We also provide estimated systematic errors due to the uncertainties of the progenitor.
Highlights
In 1987, a core-collapse supernova known as Supernova 1987A (SN1987A) was observed in the Large Magellanic Cloud
We plot the luminosity4 as a function of QCD axion mass times reduced coupling in figure 10, and we show the corresponding excluded regions of the axion mass times reduced coupling in figure 11
We have considered constraints derived from the duration of the neutrino cooling phase of SN1987A on two broad classes of dark matter (DM) particles: a dark sector fermion coupled to a kinetically mixed dark photon, as well as the QCD axion and axion-like particles
Summary
In 1987, a core-collapse supernova known as Supernova 1987A (SN1987A) was observed in the Large Magellanic Cloud. SN1987A provided a wealth of information on the supernova explosion itself and sets unique constraints on the existence of new, low-mass particles that are weakly-coupled to the Standard Model (SM) [1, 2]. The existence of new, weakly-coupled particles could provide novel channels to “cool” the proto-neutron star and change the neutrino emission from SN1987A. We will derive constraints from SN1987A on several possible low-mass particles: various dark sectors consisting of dark matter (DM) and dark photons (including millicharged particles), the QCD axion, and axion-like particles with Yukawa couplings. We will consider “light”, inelastic DM, in which the dark-sector consists of two “DM” particles, χ1 and χ2, which have a small mass splitting, and for which the interaction with the dark photon is off-diagonal, i.e. We leave many details of our calculations to various appendices
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