Weird Mesons

Physicists in Japan have discovered an odd new particle, the latest in a string of odd particles made up of quarks and gluons. This newest member is a hybrid meson, consisting of a quark, an antiquark, and a gluon. (All previous mesons have consisted of a quark and an antiquark.) The quarks are of the charmed flavor, and the resulting meson is called Y(3940), where the number represents its mass in MeV. This strange type of meson, first predicted twenty-five years ago (1978), joins the pentaquark and the 4-quark X particle as new additions to the unexpected family of weird mesons.