Spectroscopy, lifetime and decay modes of the $T^-_{bb}$ tetraquark

International audienceWe present the first full-fledged study of the flavor-exotic isoscalar Tbb−≡bbu¯d¯ tetraquark with spin and parity JP=1+ . We report accurate solutions of the four-body problem in a quark model, characterizing the structure of the state as a function of the ratio MQ/mq of the heavy to light quark masses. For such a standard constituent model, Tbb− lies approximately 150 MeV below the strong decay threshold B−B⁎¯0 and 105 MeV below the electromagnetic decay threshold B−B¯0γ . We evaluate the lifetime of Tbb− , identifying the promising decay modes where the tetraquark might be looked for in future experiments. Its total decay width is Γ≈87×10−15 GeV and therefore its lifetime τ ≈ 7.6 ps. The promising final states are B⁎−D⁎+ℓ−ν¯ℓ and B⁎¯0D⁎0ℓ−ν¯ℓ among the semileptonic decays, and B⁎−D⁎+Ds⁎− , B⁎¯0D⁎0Ds⁎− , and B⁎−D⁎+ρ− among the nonleptonic ones. The semileptonic decay to the isoscalar JP=0+ tetraquark Tbc0 is also relevant but it is not found to be dominant. There is a broad consensus about the existence of this tetraquark, and its detection will validate our understanding of the low-energy realizations of Quantum Chromodynamics (QCD) in the multiquark sector