Measurements of direct CP violation in charm decays at LHCb

Two searches for direct CP violation in D 0 ! h h + (where h = K or ) are presented using data corresponding to an integrated luminosity of 1.0 fb 1 collected in 2011 by LHCb in pp collisions at a centre-of-mass energy of 7 TeV. One analysis uses D 0 mesons produced via a D resonance and the other analysis uses D 0 mesons originating from semileptonic b - decays. In the rst case the avour is tagged by the charge of the accompanying pion and in the latter by the muon charge. The dierence of the CP -violating asymmetries ( A CP = A CP ( K K + ) A CP ( + )) in the two decay channels is measured to be A CP (muon tagged) = (0 : 49 0 : 30 (stat) 0 : 14 (syst))% ; A CP (pion tagged) = ( 0 : 35 0 : 15 (stat) 0 : 10 (syst))% ; A CP (LHCb) = ( 0 : 15 0 : 16)% : These results do not conrm evidence for CP violation in the charm sector