For Publisher’s use RESULTS ON CP VIOLATION FROM THE NA48 EXPERIMENT AT CERN.pdfVIP

For Publisher’s use RESULTS ON CP VIOLATION FROM THE NA48 EXPERIMENT AT CERN LYDIA ICONOMIDOU-FAYARD LAL, Universit´e d’Orsay, bˆat. 200, 91898 Orsay, France ON BEHALF OF THE NA48 COLLABORATION NA48 is a Cagliari, Cambridge, CERN, Dubna, Edinburgh, Ferrara, Firenze, Mainz, Orsay, Perugia, Pisa, Saclay, Siegen, Torino, Vienna and Warsaw collaboration In this article the current status and latest results of the NA48 experiment at CERN are given. We ′ present in more details the analysis performed for the Re(ε /ε) measurement with the combined statis- tics accumulated during the 1998 and 1999 data periods. Reviewing the NA48 rare decay program, we select to underline the new results on the branching ratio and the aV factor for the decay KL → π0γγ + − + − and the KL→π π e e CP violating decay. 1 Introduction Standard Model. 1.1 The NA48 experiment at CERN 1.2 CP Violation in neutral kaons The main goal of NA48 is the precise mea- A small non-conservation of the CP sym- ′ surement of Re(ε /ε) in the neutral kaon sys- metry manifests in the neutral kaon system tem. In order to achieve an accuracy of through the observation of the forbidden de- ∼ 2 × 10−4 the optimization of the detector cay mode KL→ 2π . Shortly after the dis- and beams has been conceived to allow the covery 2 the standard Model described theo- minimisation of the sensitivity to systematic reticaly the phenomenon 3 : the bulk of CP