The scientists claim they discovered a four-quark particle, or tetraquark, composed of a charm, anti-charm, down, and an anti-up quark. The particle would appear to be roughly (or possibly even exactly) a bound state of two mesons, that is two pairs of color-anticolor quarks; for example red-antired and blue-antiblue. The charges of the charm and anti-charm obviously cancel, leaving -1⁄3 from the down and -2⁄3 from the anti-up, for a total charge of -1.
I can't speak to the quality of this research per se, but I do remember the excitement and subsequent let down over the pentaquark, so I'm going to wait to hear what the wider particle physics community concludes about this latest finding. Still, it's a pretty cool finding.
