A new measurement of direct CP violation by the NA48 experiment

by Guillaume Unal (LAL-Orsay)

Thursday 10 May 2001, 16:30 → 17:30 Europe/Zurich

500/1-001 - Main Auditorium (CERN)

CP violation in the neutral kaon system is known to be dominated by the mixing of K⁰ and K⁰bar eigenstates. Direct CP violation in 2 pion decays of neutral kaons has been a controversial subject in the last decade. While its existence is now established, the size of the effect is still not well known. The parameter e'/e, giving the value of direct CP violation, is derived from the double ratio of the decay rates of long lived (K_L) and short lived (K _S) neutral kaons to two charged and two neutral pions. The NA48 experiment is designed to minimize systematic uncertainties: simultaneous K _L and K _S beams are used, the decay region is the same for all modes, and the 2 pion final states are identified by high resolution detectors. During 1998 and 1999, 3 million of the most suppressed decay mode K _L to two neutral pions have been collected. The measurement of e'/e from this data set will be presented. The accuracy is +-2.6 x10 ^-4, significantly improving previous measurements.

Organiser(s): Jasper Kirkby / EP Division

Note: * Tea & coffee will be served at 16.00 hrs.