“School of Particles And Accelerator”
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Paper IPM / Particles And Accelerator / 15651  


Abstract:  
We study semileptonic decays of the scalar tetraquark Z_{bc;―u―d}^{0} to final states T_{bs;―u―d}^{−}e^{+}ν_{e} and T_{bs;―u―d}^{−}μ^{+}ν_{μ}, which run through the weak transitions c→ se^{+}ν_{e} and c→sμ^{+}ν_{μ}, respectively. To this end, we calculate the mass and
coupling of the finalstate scalar tetraquark T_{bs;―u―d}^{−} by means of the QCD twopoint sum rule method: these spectroscopic
parameters are used in our following investigations. In calculations we take
into account the vacuum expectation values of the quark, gluon, and mixed
operators up to dimension ten. We use also threepoint sum rules to evaluate
the weak form factors G_{i}(q^{2}) (i=1, 2) that describe these decays.
The sum rule predictions for G_{i}(q^{2}) are employed to construct fit
functions F_{i}(q^{2}), which allow us to extrapolate the form factors to
the whole region of kinematically accessible q^{2}. These functions are
required to get partial width of the semileptonic decays Γ(Z_{bc}^{0}→ Te^{+}ν_{e}) and Γ(Z_{bc}^{0}→ Tμ^{+}ν_{μ}) by integrating
corresponding differential rates. The obtained results for the total width Γ_{tot.}=(2.37±0.36)×10^{−11} MeV and mean
lifetime 27.8_{−3.7}^{+4.9} ps of the tetraquark Z_{bc;―u―d}^{0} can be used in experimental investigations of this
exotic state.
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