Semileptonic decays of the scalar tetraquark

H. Sundu; S. S. Agaev; K. Azizi

doi:10.1140/epjc/s10052-019-7268-4

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2019) 79: 753
https://doi.org/10.1140/epjc/s10052-019-7268-4

Regular Article - Theoretical Physics

Semileptonic decays of the scalar tetraquark $Z_{bc;\overline{u}\overline{d}}^{0}$

H. Sundu¹, S. S. Agaev² and K. Azizi³^,4^,5^*

¹ Department of Physics, Kocaeli University, 41380, Izmit, Turkey
² Institute for Physical Problems, Baku State University, Az1148, Baku, Azerbaijan
³ Department of Physics, University of Tehran, North Karegar Ave., Tehran, 14395-547, Iran
⁴ Department of Physics, Doǧuş University, Acibadem-Kadiköy, 34722, Istanbul, Turkey
⁵ School of Particles and Accelerators, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran, Iran

^* e-mail: kazem.azizi@ut.ac.ir

Received: 14 July 2019
Accepted: 2 September 2019
Published online: 10 September 2019

Abstract

We study semileptonic decays of the scalar tetraquark $Z_{bc;\overline{u} \overline{d}}^{0}$ to final states $T_{bs;\overline{u}\overline{d} }^{-}e^{+}\nu _{e}$ and $T_{bs;\overline{u}\overline{d}}^{-}\mu ^{+}\nu _{\mu }$ , which run through the weak transitions $c\rightarrow se^{+}\nu _{e}$ and $c\rightarrow s\mu ^{+}\nu _{\mu }$ , respectively. To this end, we calculate the mass and coupling of the final-state scalar tetraquark $T_{bs;\overline{u}\overline{d} }^{-}$ by means of the QCD two-point 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 three-point 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 widths of the semileptonic decays $\Gamma \left( Z_{bc}^{0}\rightarrow Te^{+}\nu _{e}\right)$ and $\Gamma \left( Z_{bc}^{0}\rightarrow T\mu ^{+}\nu _{\mu }\right)$ by integrating corresponding differential rates. We analyze also the two-body nonleptonic decays $Z_{bc;\overline{u}\overline{d}}^{0} \rightarrow T_{bs;\overline{u}\overline{d }}^{-}\pi ^{+}$ and $Z_{bc;\overline{u}\overline{d}}^{0} \rightarrow T_{bs;\overline{u }\overline{d}}^{-}K^{+}$ , which are necessary to evaluate the full width of the $Z_{bc;\overline{u}\overline{d}}^{0}$ . The obtained results for $\Gamma _{\mathrm {full}}=(3.18\pm 0.39)\times 10^{-11}~{\mathrm {MeV}}$ and mean lifetime $20.7_{-2.3}^{+2.9}~{\mathrm {ps}}$ of the tetraquark $Z_{bc;\overline{u} \overline{d}}^{0}$ can be used in experimental investigations of this exotic state.