Physicists create 'Bethe strings' predicted in 1931

Researchers at the University of Innsbruck have created and observed 'Bethe strings' — multiparticle bound states predicted by Hans Bethe in 1931. Using ultracold cesium atoms confined to one-dimensional tubes, they showed clusters of six or more particles can collide without breaking apart. The results were published in Nature Communications.

• Bethe strings were predicted by Hans Bethe in 1931
• Cesium atoms were cooled to billionths of a degree above absolute zero
• Clusters of six or more particles survived collisions
• Bound states fell apart when released into three dimensions