Signature decay modes of the compact doubly-heavy tetraquarks Tbbū d̄ and Tbcū d̄

Based on the expectations that the lowest-lying double-bottom tetraquark Tbb u d (JP=1⁺) and the bottom-charm tetraquark Tbc u d (JP=0⁺) are stable against strong and electromagnetic decays, we work out a number of semileptonic and non-leptonic weak decays of these hadrons, making use of the heavy quark symmetry. In doing this, we concentrate on the exclusive decays involving also tetraquarks in the final states, i.e., transitions such as Tbb u d → Tbc u d (⁻ ν_, h⁻) and Tbc u d → Tcc u d (⁻ ν_, h⁻), where h⁻=π⁻,ρ⁻,a₁⁻. So far, only the JP=1⁺ tetraquark Tcc u d has been discovered, which we identify with the $I=0$ Tcc⁺ object, compatible with JP=1⁺ and having the mass and decay widths δ m =M(Tcc⁺) -(M(D*+) - M(D⁰))= -360 ± 40 ⁺⁴₋₀ keV and Γ(Tcc⁺)=48⁺²₋₁₄ keV. Experimental discoveries of the transitions worked out here will go a long way in establishing the nature of these tetraquarks as (mainly) compact four-quark objects.