Speaker
Description
Abstract: A light CP-even scalar $S$ with mass below GeV-scale exists in may beyond standard model (SM) scenarios. Such a light particle can be produced abundantly in the stars, such as the Sun, red giants, white dwarfs, horizontal-branch stars, neutron star mergers, and supernovae. In this talk I will show the state-of-art stellar limits on $S$. Assuming the couplings of $S$ to the SM particles are from mixing with the SM Higgs, the production of $S$ will be dominated by nucleon bremsstrahlung process in all the stars. With the decay and reabsorption of $S$ taken into consideration, the stellar luminosities exclude a broad range of the mixing angle, from $7.0 \times 10^{-18}$ to $3.4 \times 10^{-3}$, with the scalar mass up to roughly order of 100 MeV. These stellar limits are largely complementary to other laboratory, astrophysical and cosmological limits on $S$.
