2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/200577Recent results by BELLE and BaBar point to the existence of a second X particle decaying in D^0 D^0bar pi^0, a few MeV above the X(3872). We identify the two X states with the neutral particles predicted by the 4-quark model and show that production and decays are consistent with this assignement. We consider the yet-to-be-observed charged partners and give new hints on how to look for them.5 pages, some revision of the text, results unchanged. To appear in Phys. Rev. LettHigh Energy Physics - Phenomenologytext