Abstract
Recently, Weinberg proposed a scenario where Goldstone bosons may be masquerading as fractional cosmic neutrinos. We calculate the energy loss rates through the emission of these Goldstone bosons in a post-collapse supernova core. Invoking the well established emissivity bound from the Supernova 1987A observations and simulations, we find that nuclear bremsstrahlung processes can notably impose a bound on the Goldstone boson coupling to the Standard Model Higgs, $g$, dependent on the mass of the associated radial field, $m_r$. For $m_r$ large enough compared with the temperature in the post-collapse supernova core, our bound is $|g| \lesssim 0.011\, (m_r / 500~{\rm MeV})^2$, very competitive to that derived from collider experiments.
Highlights
The WMAP9 data combined with eCMB, BAO, and H0 measurements has inferred Nν = 3.55+−00..4498 at 68% CL [1]
We have determined the allowed range for the coupling constant g in dependence of mr, the mass of the radial field r(x) in Weinberg’s extended Higgs model, in which new Goldstone bosons may be masquerading as fractional cosmic neutrinos
We present our main result in Eq (25), obtained by confronting our estimate for the nuclear bremsstrahlung processes with the well established emissivity bound from the Supernova 1987A
Summary
The cosmic microwave background (CMB) radiation, if combined with other observational data, can be used to constrain the effective number of light neutrino species. A simple extended Higgs sector in the Standard Model (SM) has been proposed to realize this idea such that the Goldstone bosons contribute significantly to the effective number of light species. The thermal history of these Goldstone bosons depends crucially on their coupling to the Standard Model Higgs field and the mass of the radial field. In Eq (3), we have replaced α(x) → α(x)/(2 r ) in order to achieve a canonical kinetic term for the α(x) field In this model, the interaction of the Goldstone bosons with the SM particles arises entirely from a mixing of the radial boson with the Higgs boson via the mixing angle tan 2θ.
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