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Recent investigations have suggested that the six-quark combination uuddss could be a deeply bound state (S) that has eluded detection so far, and a potential dark matter candidate. We report the first search for a stable, doubly strange six-quark state in ϒ → SΛ¯ Λ¯ decays based on a sample of 90 × 106ϒ(2S) and 110 × 106ϒ(3S) decays collected by the BABAR experiment. No signal is observed, and 90% confidence level limits on the combined ϒ(2S; 3S) → SΛ¯ Λ¯ branching fraction in the range (1.2–1.4) × 10−7 are derived for mS < 2.05 GeV. These bounds set stringent limits on the existence of such exotic particles.

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Lees, J. P., Poireau, V., Tisserand, V., Grauges, E., Palano, A., Eigen, G., Brown, D. N., Kolomensky, Yu. G., Fritsch, M., Koch, H., Schroeder, T., Hearty, C., Mattison, T. S., McKenna, J. A., So, R. Y., Blinov, V. E., Buzykaev, A. R., Druzhinin, V. P., Golubev, V. B., … Wu, S. L. (2019). Search for a stable six-quark state at Babar. Physical Review Letters, 122(7).

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