Andrew Watson
A new detector on the HERA positron-proton collider in Hamburg, Germany, has confirmed a long-standing puzzle about the toplike spin of protons and neutrons--and physicists are delighted. The puzzle is that the quarks that make up protons and neutrons don't contribute nearly enough spin to explain the total. By confirming the shortfall, the new detector, called HERMES, has shown that its sophisticated spin-probing technology is working properly--and may eventually be able to track down the missing spin.