Delta ACP within the Standard Model and beyond

Abstract

In light of the recent LHCb observation of CP violation in the charm sector, we review standard model (SM) predictions in the charm sector and in particular for ∆ACP. We get as an upper bound in the SM |∆ASM CP| ≤ 3.6 × 10−4 , which can be compared to the measurement of ∆ALHCb2019 CP = (−15.4 ± 2.9) × 10−4 . We discuss resolving this tension within an extension of the SM that includes a flavour violating Z 0 that couples only to ¯ss and ¯cu. We show that for masses below 80 GeV and flavour violating coupling of the order of 10−4 , this model can successfully resolve the tension and avoid constraints from dijet searches, D0 − D 0 mixing and measurements of the Z width.