Spectroscopy, lifetime and decay modes of the T b b ? tetraquark

摘要

We present the first full-fledged study of the flavor-exotic isoscalarTbb?≡bbuˉdˉtetraquark with spin and parityJP=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 ratioMQ/mqof the heavy to light quark masses. For such a standard constituent model,Tbb?lies approximately 150 MeV below the strong decay thresholdB?B?ˉ0and 105 MeV below the electromagnetic decay thresholdB?Bˉ0γ. We evaluate the lifetime ofTbb?, identifying the promising decay modes where the tetraquark might be looked for in future experiments. Its total decay width isΓ≈87×10?15GeV and therefore its lifetimeτ≈ 7.6 ps. The promising final states areB??D?+??νˉ?andB?ˉ0D?0??νˉ?among the semileptonic decays, andB??D?+Ds??,B?ˉ0D?0Ds??, andB??D?+ρ?among the nonleptonic ones. The semileptonic decay to the isoscalarJP=0+tetraquarkTbc0is 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.