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

• Main Authors: Ali, Ahmed, Maiani, Luciano, Parkhomenko, Alexander Ya, Wang, Wei
• Format: Journal Article
• Language: English
• Published: 16-10-2019
• Subjects: Physics - High Energy Physics - Experiment; Physics - High Energy Physics - Phenomenology
• DOI: 10.48550/arxiv.1910.07671

Physics Letters B 802 (2020) 135217 Recently, the Belle Collaboration has updated the analysis of the cross
sections for the processes $e^+ e^- \to \Upsilon(nS)\, \pi^+ \pi^-$ ($n = 1,\,
2,\, 3$) 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 $M (Y_b) = (10752.7
\pm 5.9^{+0.7}_{-1.1})$ MeV and the Breit-Wigner width $\Gamma (Y_b) =
(35.5^{+17.6 +3.9}_{-11.3 -3.3})$ 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 $\Upsilon(5S)$ 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 $p p \to Y_b
(10750) \to \Upsilon (nS)\, \pi^+ \pi^-$ at the LHC. The resonant part of the
dipion invariant mass spectrum in $Y_b (10750) \to \Upsilon (1S)\, \pi^+ \pi^-$
and the corresponding angular distribution of $\pi^+$-meson in the dipion rest
frame are presented as an example.