D

ABSTRACT

The X(3872), whose mass coincides with the D^{0}D[over ¯]^{*0} threshold, is the most extended hadron object. Since its discovery in 2003, debates have never stopped regarding its internal structure. We propose a new object, the X atom, which is the D^{±}D^{*∓} composite system with positive charge parity and a mass of (3879.89±0.07) MeV, formed mainly due to the Coulomb force. We show that a null signal of the X atom can be used to put a lower limit on the binding energy of the X(3872). From the current knowledge of the X(3872) properties, the production rate for the X atom relative to the X(3872) in B decays and at hadron colliders should be at least 1×10^{-3}. New insights into the X(3872) will be obtained through studying the X atom.