Double charmonium production in exclusive bottomonium decays

Exclusive bottomonium decays leading to the production of charmonium pairs are considered. The respective decay widths are calculatedwithin the approach of line-cone expansion for the amplitude and nonrelativistic QCD. It is shown that the production of L _z ≠ 0 P-wave charmonium states is possible even in the leading-twist approximation. This means a violation of selection rules that require the suppression of such decays. The reason for this violation is discussed in detail.