No abstract

Two tetraquark candidates Z b (10610) and Z b (10650) with flavor structurebbdu were discovered by Belle experiment in 2011. We present a preliminary N f = 2 lattice study of thebbdu system in the approximation of static b quarks, where the total spin of heavy quarks is fixed to one. The ground and the excited eigen-energies are determined as a function of separation r between b and b. The lower eigenstates are related to a bottomonium and a pion. One of the higher eigenstates is dominated by BB * : its energy is significantly below m B + m B * for r=[0.1,0.4] fm, which suggests sizable attraction. The attractive potential V (r) between B andB * is extracted assuming that this eigenstate is related exclusively to BB *. Assuming a certain form of the potential at small r < 0.1 fm and solving non-relativistic Schrodinger equation, we find a virtual bound state pole 32 −29 +5 MeV below BB * threshold. This pole leads to a narrow peak in the cross-section just above threshold that could be perhaps related to experimental Z b resonances. Given all these approximations, we surprisingly find also a deep bound state 403 ± 70 MeV below BB * threshold. If such a Z b state exists, it could be experimentally searched in the accurate dependence of rates on ϒ(1S)π + invariant mass.

Two tetraquark candidates Z b (10610) and Z b (10650) with flavor structure bb du were discovered by Belle experiment in 2011. We present a preliminary N f = 2 lattice study of the bb du system in the approximation of static b quarks, where the total spin of heavy quarks is fixed to one. The ground and the excited eigen-energies are determined as a function of separation r between b and b. The lower eigenstates are related to a bottomonium and a pion. One of the higher eigenstates is dominated by B B * : its energy is significantly below m B + m B * for r=[0.1,0.4] fm, which suggests sizable attraction. The attractive potential V (r) between B and B * is extracted assuming that this eigenstate is related exclusively to B B * . Assuming a certain form of the potential at small r < 0.1 fm and solving non-relativistic Schrodinger equation, we find a virtual bound state pole 32 −29 +5 MeV below B B * threshold. This pole leads to a narrow peak in the cross-section just above threshold that could be perhaps related to experimental Z b resonances. Given all these approximations, we surprisingly find also a deep bound state 403 ± 70 MeV below B B * threshold. If such a Z b state exists, it could be experimentally searched in the accurate dependence of rates on ϒ(1S)π + invariant mass.