Theta Term in QCD sum rules at Finite Temperature and the Neutron Electric Dipole Moment

Abstract

By using thermal QCD sum rules to investigate the $\bar{\theta }$ induced neutron electric dipole moment $d_n$, we have examined the behaviour of broken CP symmetry at finite temperature. We find that, below the critical temperature, the ratio $\mid \frac{d_n}{\bar{\theta }}\mid$ slightly decreases but survives at temperature effects, implying T nonrestoration of CP-invariance \cite{Chabab}.

Comments: 08pages, Latex, Invited Tall given at the Second International Workshop on Hadron Physics, Effective Theories of Low Energy QCD, 25-29 September, 2002 (Coimbra, Portugal); to appear in the proceedings