Strange Mesonic Atoms Detected

An atom is normally a nucleus surrounded by electrons. But physicists have observed several exotic atoms comprising other particles, such as mesons (two-quark particles). Following earlier hints, a new analysis of data from the DIRAC experiment at CERN finds the first conclusive evidence of an atom made up of a pi meson (containing up and down quarks) and a k meson (containing up and strange quarks). Further study of these strange dimesons should give insight into how quarks interact at relatively low energies.