From one of the articles linked in in the HN comments [0]: > The particles, known as the Xi_b'- and Xi_b-, were predicted to exist by the quark model but had n

From one of the articles linked in in the HN comments [0]: > The particles, known as the Xi_b'- and Xi_b-, were predicted to exist by the quark model but had never been seen before. A related particle, the Xi_b0, was found by the CMS experiment at CERN in 2012. The LHCb collaboration submitted a paper reporting the finding to Physical Review Letters.* 0: http://home.web.cern.ch/about/updates/2014/11/lhcb-observes-two-new-baryon-particles http://home.web.cern.ch/about/updates/2014/11/lhcb-observes-... * some of the formatting of the particle names got borked by the HN comment system limitations--I tried using <sup> tags but they don't appear to work. The correct spelling/representation of the particle names can be found in [0]