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

TL;DR

This study searches for double charmonium decays of P-wave bottomonium states using Belle data, setting upper limits that challenge some theoretical models but align with others.

Contribution

First experimental search for these specific double charmonium decays in bottomonium states, providing new upper limits that constrain theoretical predictions.

Findings

No significant signals observed.

Upper limits are lower than some theoretical predictions.

Results are consistent with NRQCD calculations.

Abstract

Using a sample of 158 million $\Upsilon(2S)$ events collected with the Belle detector, we search for the first time for double charmonium decays of the $P$-wave spin-triplet bottomonium states ($\Upsilon(2S) \to \gamma \chi_{bJ}$, $\chi_{bJ} \to \jpsi \jpsi$, $\jpsi \psp$, $\psp \psp$ 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, $\BR(\chi_{bJ} \to \jpsi \jpsi)<7.1\times 10^{-5}$, $2.7\times 10^{-5}$, $4.5\times 10^{-5}$, $\BR(\chi_{bJ} \to \jpsi \psp)<1.2\times 10^{-4}$, $1.7\times 10^{-5}$, $4.9\times 10^{-5}$, $\BR(\chi_{bJ} \to \psp \psp)<3.1\times 10^{-5}$, $6.2\times 10^{-5}$, $1.6\times 10^{-5}$ 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.