Bose-Einstein correlations

Bose-Einstein Correlations are studied since a long time in high energy physics, but are still poorly understood. As this e.ect can be a source of large systematic error in W mass measurement in the WW → q1q-bar2 q3q-bar4 channel, new studies are made by the four LEP experiments, both using the Z peak data (from LEP1)and the W pairs data (from LEP2). Also, looking at these correlations in W pair events gives an insight on the simultaneous hadronization of two color strings. The analyses performed by the four LEP collaborations are presented. In the WW →q1q-bar2 q3q-bar4 channel, a consistent picture of no correlations between the decay products of the two Ws seems to emerge. (author)