Testing $CPT$ invariance with the neutral-$D$ system

Abstract

We investigate the issue of testing CPT invariance in the neutral-D system, using D events obtained either from fixed-target experiments or from a τ-charm factory. For both types of experiments we show that the expected suppression of mixing in the D system, normally viewed as a disadvantage for CP tests, allows unsuppressed measurement of certain parameters describing CPT violation. Asymmetries are presented that permit the extraction of parameters for direct CPT violation in the D system and for indirect CPT violation in the K system. We also show that experiments on the neutral-D system provide an alternative means for measuring conventional indirect T violation in the kaon system.