Abstract
In this work, we propose the possible assignment of the newly observed , as well as , as a molecular state from the interaction of a baryon and an antibaryon . With the help of effective Lagrangians, the interaction is described within the one-boson-exchange model with , , , , and exchanges considered. After inserting the potential kernel into the quasipotential Bethe-Salpeter equation, the bound states from the interaction can be studied by searching for the pole of the scattering amplitude. Two loosely bound states with spin parities and appear near the threshold with almost the same parameter. The state can be assigned to observed at BESIII, which is very close to the threshold. The scalar meson can be interpreted as a state from the interaction. The annihilation effect is also discussed through a coupled-channel calculation plus a phenomenological optical potential. It provides large widths to two bound states produced from the interaction. The mass of the state is slightly larger than the mass of the state after including the annihilation effect, which is consistent with our assignment of these two states as and , respectively. The results suggest that further investigation is required to understand the structures near the threshold, such as , , and .
Highlights
After the observation of X(3872) at Belle, more and more XYZ particles were reported at different experimental facilities, and attract great interest from theoretical side [1]
The molecular state composed of a baryon and an antibaryon is an interesting topic in the study of exotic mesons
We study the possibility to assign the newly observed X(2239) as a ΛΛmolecular state in the quasipotential Bethe-Salpeter (qBSE) approach
Summary
After the observation of X(3872) at Belle, more and more XYZ particles were reported at different experimental facilities, and attract great interest from theoretical side [1]. The possible molecular states are widely discussed theoretically and applied to explain the observed exotic hadrons. Even before proposition of the quark model, the possibility to interpret π meson as a NNbound state was discussed by Fermi and Yang [26] Such attempt is incorrect based on later studies, and was abandoned soon. [53], which was done before the observation of X(2239) at BESIII, the Y(2175) and η(2225) can be interpreted as ΛΛ (3S 1) and ΛΛ (1S 0) molecular states, respectively, which is the first attempt to discuss the possible molecular state from the ΛΛinteraction. The theoretical values of the mass will deviate from the one within the one-boson-exchange model, and the bound state will acquire a width after the annihilation effect is included.
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