Top quarks spin together more than they should, according to new ATLAS result
(PHYSorg.com Physics)

The top quark is a unique particle due to its phenomenally high mass. It decays in less than 10 to 24 seconds, before it has time to interact with any other particles. Therefore, many of its quantum numbers, such as its spin, are transferred to its decay particles. When created in matter-antimatter pairs, the spins of the top quark and the antitop quark are expected to be correlated to some degree.