Can heavy-ion collisions cast light on strong CP?

by Panos Christakoglou. Published: 19 February 2013

The symmetries of parity (P) and its combination with charge conjugation (C) are known to be broken in the weak interaction. However, in the strong interaction the P and CP invariances are respected – although QCD provides no reason for their conservation. This is the "strong CP problem", one of the remaining puzzles of the Standard Model.