Interpretation of $Y_b(10750)$ as a tetraquark and its production mechanism

Abstract

Recently, the Belle Collaboration has updated the analysis of the cross sections for the processes $e^{+}{e}^{-}\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ ($n=1,2,3$) in the $e^{+}{e}^{-}$ center-of-mass energy range from 10.52 to 11.02 GeV. A new structure, called here $Y_b(10750)$, with the mass $M(Y_b)=(10752.7\pm 5.9_{-1.1}^{+0.7})$ MeV and the Breit-Wigner width $\Gamma (Y_b)=(35.5_{-11.3-3.3}^{+17.6+3.9})$ MeV was observed \cite{Abdesselam:2019gth}. We interpret $Y_b(10750)$ as a compact $J^{PC}=1^{--}$ state with a dominant tetraquark component. The mass eigenstate $Y_b(10750)$ is treated as a linear combination of the diquark-antidiquark and $b\bar{b}$ components due to the mixing via gluonic exchanges shown recently to arise in the limit of large number of quark colors. The mixing angle between $Y_b$ and ${\rm Y}(5S)$ can be estimated from the electronic width, recently determined to be ${\Gamma }_{ee}(Y_b)=(13.7\pm 1.8)$ eV. The mixing provides a plausible mechanism for $Y_b(10750)$ production in high energy collisions from its $b\bar{b}$ component and we work out the Drell-Yan and prompt production cross sections for $pp\to Y_b(10750)\to {\rm Y}(nS){\pi }^{+}{\pi }^{-}$ at the LHC. The resonant part of the dipion invariant mass spectrum in $Y_b(10750)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-}$ and the corresponding angular distribution of ${\pi }^{+}$-meson in the dipion rest frame are presented as an example.

6 pages, 3 figures; v2: some numerics updated based on new results for ${\Gamma }_{ee}(Y_b)$, references added; v3: accept by Physics Letters B

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• Hadronic cross section of $e^{+}{e}^{-}$ annihilation at bottomonium energy region
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• Heavy hybrid decays to quarkonia
• Study of $I=0$ bottomonium bound states and resonances in $S$, $P$, $D$ and $F$ waves with lattice QCD static-static-light-light potentials
• Hidden-bottom hadronic transitions of ${\rm Y}(10753)$
• Mass spectrum of $1^{--}$ heavy quarkonium
• Status and Prospects of Exotic Hadrons at Belle II
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• Predictions for Bottomonium from a Relativistic Screened Potential Model
• Decays of ${\rm Y}(10860)$ and ${\rm Y}(10753)$ into $\omega {\chi }_{bJ}$
• Improved measurement of Born cross sections for ${\chi }_{bJ}\omega$ and ${\chi }_{bJ}({\pi }^{+}{\pi }^{-}{\pi }^0{)}_{\mathrm{non}-\omega }$ ($J$ = 0, 1, 2) at Belle and Belle II
• Exotic hadrons associated with $b$-quark
• Search for $e^{+}{e}^{-}\to \gamma {\chi }_{bJ}$ ($J$ = 0, 1, 2) near $\sqrt{s}=10.746$ GeV at Belle II