Stellar limits on light CP-even scalar
P.S. Bhupal Dev, Rabindra N. Mohapatra, Yongchao Zhang
Abstract
Abstract We revisit the astrophysical constraints on a generic light CP-even scalar particle S , mixing with the Standard Model (SM) Higgs boson, from observed luminosities of the Sun, red giants, white dwarfs and horizontal-branch stars. The production of S in the stellar core is dominated by the electron-nuclei bremsstrahlung process e + N → e + N + S . With the S decay and reabsorption processes taken into consideration, we find that the stellar luminosity limits exclude a broad range of parameter space in the S mass-mixing plane, with the scalar mass up to 350 keV and the mixing angle ranging from 7.0 × 10 -18 to 3.4 × 10 -3 . We also apply the stellar limits to a real-singlet scalar extension of the SM, where we can relate the mixing angle to the parameters in the scalar potential. In both the generic scalar case and the real-singlet extension, we show that the stellar limits preclude the scalar interpretation of the recently observed XENON1T excess in terms of the S particles emitted from the Sun.