2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/177839The effects of charmed meson loops on the spectrum of charmonium are considered, with special attention paid to the levels above open-charm threshold. It is found that the coupling to charmed mesons generates a structure at the D \bar{D}* threshold in the 1++ partial wave. The implications for the nature of the X(3872) state are discussed.27 pages, 7 EPS figuresHigh Energy Physics - Phenomenologytext