Search for double charmonium decays of the P-wave spin-triplet bottomonium states

Abstract

Using a sample of 158 million ${\rm Y}(2S)$ events collected with the Belle detector, we search for the first time for double charmonium decays of the $P$-wave spin-triplet bottomonium states (${\rm Y}(2S)\to \gamma {\chi }_{bJ}$, ${\chi }_{bJ}\to \text{jpsi}\text{jpsi}$, $\text{jpsi}\text{psp}$, $\text{psp}\text{psp}$ for J=0, 1, and 2). No significant ${\chi }_{bJ}$ signal is observed in the double charmonium mass spectra, and we obtain the following upper limits, $\text{BR}({\chi }_{bJ}\to \text{jpsi}\text{jpsi})<7.1\times 10^{-5}$, $2.7\times 10^{-5}$, $4.5\times 10^{-5}$, $\text{BR}({\chi }_{bJ}\to \text{jpsi}\text{psp})<1.2\times 10^{-4}$, $1.7\times 10^{-5}$, $4.9\times 10^{-5}$, $\text{BR}({\chi }_{bJ}\to \text{psp}\text{psp})<3.1\times 10^{-5}$, $6.2\times 10^{-5}$, $1.6\times 10^{-5}$ for J=0, 1, and 2, respectively, at the 90% confidence level. These limits are significantly lower than the central values (with uncertainties of 50% to 70%) predicted using the light cone formalism but are consistent with calculations using the NRQCD factorization approach.

Comments: 7 pages, 4 figures, 1 table