Hunting for the Xb via radiative decays

In this paper, we study radiative decays of XbXb, the counterpart of the famous X(3872)X(3872) in the bottomonium-sector as a candidate for meson–meson molecule, into the γϒ(nS)γϒ(nS) (n=1,2,3n=1,2,3). Since it is likely that the XbXb is below the BB¯⁎ threshold and the mass difference between the neutral and charged bottom meson is small compared to the binding energy of the XbXb, the isospin violating decay mode Xb→ϒ(nS)π+π−Xb→ϒ(nS)π+π− would be greatly suppressed. This will promote the importance of the radiative decays. We use the effective Lagrangian based on the heavy quark symmetry to explore the rescattering mechanism and calculate the partial widths. Our results show that the partial widths into γϒ(nS)γϒ(nS) are about 1 keV, and thus the branching fractions may be sizeable, considering the fact the total width may also be smaller than a few MeV like the X(3872)X(3872). These radiative decay modes are of great importance in the experimental search for the XbXb particularly at hadron collider. An observation of the XbXb will provide a deeper insight into the exotic hadron spectroscopy and is helpful to unravel the nature of the states connected by the heavy quark symmetry.