Orateur
Alessio Notari
Description
I will discuss the possibility of detecting the QCD axion as a hot relic from the early universe, if it is directly coupled to quarks, such as in DFSZ models. For sufficiently low decay constant the dominant production mechanism at temperatures 1GeV≲T≲100GeV is obtained via scatterings with heavy quarks. This leads to a contribution to the effective neutrino number, $N_eff$, which is larger than the one obtained when thermalization happens only above the electroweak phase transition, ΔNeff≲0.027. Such a prediction is within reach of future CMB S4 experiments, thus opening an alternative window to detect the QCD axion and to test the early universe at such temperatures.
Auteur principal
Alessio Notari
