Bottomonium mesons and strategies for their observation

The $B$-factories and Large Hadron Collider experiments have demonstrated the ability to observe and measure the properties of bottomonium mesons. In order to discover missing states it is useful to know their properties to develop a successful search strategy. To this end we calculate the masses and decay properties of excited bottomonium states. We use the relativized quark model to calculate the masses and wave functions and the ${{}^{3}P}_0$ quark-pair creation model to calculate decay widths to open bottom. We also summarize results for radiative transitions, annihilation decays, hadronic transitions and production cross sections which are used to develop strategies to find these states. We find that the $b\overline{b}$ system has a rich spectroscopy that we expect to be substantially extended by the LHC and $e^{+}{e}^{-}$ experiments in the near future. Some of the most promising possibilities at the LHC are observing the ${\chi }_{b(1,2)}(3P)$, ${\chi }_{b(1,2)}(4P)$ and ${\eta }_b(3S)$ states in $\gamma {\mu }^{+}{\mu }^{-}$ final states that proceed via radiative transitions through $\mathrm{\Upsilon }(nS)$ intermediate states and $1{{}^{3}D}_J$ and $2{{}^{3}D}_J$ into $\gamma \gamma {\mu }^{+}{\mu }^{-}$ final states proceeding via $1{{}^{3}P}_J\to 1{{}^{3}S}_1$ and $2{{}^{3}P}_J\to 2{{}^{3}S}_1$ intermediate states respectively. Some of the most interesting possibilities in $e^{+}{e}^{-}$ collisions are studying the $1{{}^{3}D}_J$ states via $4\gamma$ cascades starting with the $\mathrm{\Upsilon }(3S)$ and the $3{{}^{3}P}_J$ states in $\gamma \gamma {\mu }^{+}{\mu }^{-}$ final states starting with the $\mathrm{\Upsilon }(4S)$ and proceeding via $\mathrm{\Upsilon }(nS)$ intermediate states. Completing the bottomonium spectrum is an important validation of lattice QCD calculations and a test of our understanding of bottomonium states in the context of the quark model.

Figure 1

The $b\overline{b}$ mass spectrum as predicted by the relativized quark model [11].