Possible experimental signatures of stable double beauty tetraquarks.

A new method is proposed to search for the double beauty tetraquark $bb\bar{u}\bar{d}$ with a mass below the $BB$ threshold. The $b\bar{d}-\bar{b}d$ mixing can result in evolution of the tetraquark content to $b\bar{b}\bar{u}d$ with the following strong decay into the $\Upsilon$(1S)$\pi^-$ and $\Upsilon$(2S)$\pi^-$ final states in a secondary vertex displaced from the primary $pp$ collision vertex. This experimental signature is clean, has a high selection efficiency and can be well separated from backgrounds. Experimental signatures for searches for other double heavy tetraquarks are also discussed, suggesting the possibility of the $b\bar{d}$ or $b\bar{s}$ mixing.