It is the first baryon that contains quarks of all three generations, namely "dsb". Note that all of them are lower quarks, making the net charge "-1". While the evidence so far has been largely indirect (from LEP), D0-brains have found it as a 5.5 sigma bump via its decay
In other words, the probability that it is background equals 0.033 ppm. Yes, the left hand side is the new particle. See$\Xi_b^- \to J/ \psi + \Xi^-.$
PreprintIn the preprint, there is a funny typo in the list of authors. Can you find it?
Space Daily