📝 SummarXiv

Abstract

We propose a new scenario to realize the Coleman-Weinberg (CW) type chiral phase transition in the QCD thermal history. This scenario predicts an axionlike particle (ALP) with mass $\gtrsim$ sub GeV, consistently with the current experimental and cosmological bounds. The chiral phase transition is evaluated by monitoring ordinary QCD setup in a view of a two-flavor Nambu-Jona-Lasinio model at the mean-field approximation level. The present work thus can open a new window to search for the ALP associated with the QCD phase transition epoch of the thermal history, to be probed by gravitational wave and primordial black hole productions. This proposal is based on a generic classification of the order of the chiral phase transition in a view of the scale violation classes: the soft-scale breaking term and the CW-type scale anomaly term, in or off medium with or without chemical potentials. On this theoretical ground, we also revisit existing scenarios which undergo the supercooling chiral phase transition, such as nearly scale-invariant QCD and QCD with a large baryon chemical potential.