專題演講

2018/10/17(Wed)     14:00 -15:30    7th Floor(P7F)

Title

Goldstone Boson Emission From Nucleon Cooper Pairing in Neutron Stars and Constraints on the Higgs Portal Models

Speaker

Dr. Huitzu Tu

Institute of physics, Academia Sinica

Abstract

When a neutron star cools to below the critical temperature for the onset of superfluidity, nucleon pair breaking and formation (PBF) processes become the dominant mechanism for neutrino emission, while the modified URCA and the nuclear bremsstrahlung processes are suppressed. The PBF processes in neutron stars have also been used to set upper limits on the properties of axions, which are comparable to those set by supernova SN 1987A. We apply this constraint on Weinberg's Higgs portal model, in which the dark radiation particles (the Goldstone bosons) and the dark matter candidate (a Majorana fermion) interact with the Standard Model (SM) fields solely through the mixing of the SM Higgs boson and a light Higgs boson. We compare the Goldstone boson emissivity with that of the neutrinos by considering several superfluid gap models for the neutron singlet-state pairing in the neutron star inner crust, as well as in the core region. We find that the PBF processes in the superfluid neutron star interior can indeed probe Weinberg's Higgs portal model in a new parameter space region. Together with our previous works on the constraints from supernovae and gamma-ray bursts, this study demonstrates further the competitiveness and complementarity of astrophysics to laboratory particle physics experiments.