A U A ( 1 ) symmetry restoration scenario supported by the generalized Witten–Veneziano relation and its analytic solution

摘要

The Witten–Veneziano relation, or, alternatively, its generalization proposed by Shore, facilitates understanding and describing the complex of η and η ′ mesons. We present an analytic, closed-form solution to Shore's equations which gives results on the η – η ′ complex in full agreement with results previously obtained numerically. Although the Witten–Veneziano relation and Shore's equations are related, the ways they were previously used in the context of dynamical models to calculate η and η ′ properties, were rather different. However, with the analytic solution, the calculation can be formulated similarly to the approach through the Witten–Veneziano relation, and with some conceptual improvements. In the process, one strengthens the arguments in favor of a possible relation between the U A ( 1 ) and SU A ( 3 ) chiral symmetry breaking and restoration. To test this scenario, the experiments such as those at RHIC, NICA and FAIR, which extend the RHIC (and LHC) high-temperature scans also to the finite-density parts of the QCD phase diagram, should pay particular attention to the signatures from the η ′ – η complex indicating the symmetry restoration.