Measurement of exclusive ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays into Vector-Pseudoscalar final states

Abstract

Using samples of 102 million ${\rm Y}(1S)$ and 158 million ${\rm Y}(2S)$ events collected with the Belle detector, we study exclusive hadronic decays of these two bottomonium resonances to $\ks K^+ π^-$ and charge-conjugate (c.c.) states, ${\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$, and ${\pi }^{+}{\pi }^{-}{\pi }^0$, and to the two-body Vector-Pseudoscalar ($K^{\ast }(892{)}^0{\bar{K}}^0+c.c.$, $K^{\ast }(892{)}^{-}{K}^{+}+c.c.$, $\omega {\pi }^0$, and $\rho \pi$) final states. For the first time, signals are observed in the modes $Υ(1S) \to \ks K^+ π^- + {\rm c.c.}$, ${\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$, and ${\rm Y}(2S)\to {\pi }^{+}{\pi }^{-}{\pi }^0{\pi }^0$, and evidence is found for the modes ${\rm Y}(1S)\to {\pi }^{+}{\pi }^{-}{\pi }^0$, $K^{\ast }(892{)}^0{\bar{K}}^0+c.c.$, and $Υ(2S) \to \ks K^+ π^- + {\rm c.c.}$ Branching fractions are measured for all the processes, while 90% confidence level upper limits on the branching fractions are also set for the modes with a statistical significance of less than $3\sigma$. The ratios of the branching fractions of ${\rm Y}(2S)$ and ${\rm Y}(1S)$ decays into the same final state are used to test a perturbative QCD prediction for OZI-suppressed bottomonium decays.

8 pages, 3 figures, 2 tables, accepted for publication as a Rapid Communication in Physical Review D

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• PYTHIA 6.4 Physics and Manual
• Heavy quarkonium: progress, puzzles, and opportunities
• Search for charmonium and charmonium-like states in Υ(2S) radiative decays
• Exclusive processes $e^{+}{e}^{-}\to VP$ in $k_T$ factorization
• First observation of exclusive ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays into light hadrons
• First Measurements of Exclusive Hadronic Decays of Upsilon(1S) and Upsilon(2S)

Cited by in corpus (6)

• Measurement of $e^{+}{e}^{-}\to \omega {\pi }^0$, $K^{\ast }(892)\bar{K}$ and $K_2^{\ast }(1430)\bar{K}$ at $\sqrt{s}$ near 10.6 GeV
• Search for the $0^{--}$ Glueball in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays
• Impact of the interference between the resonance and continuum amplitudes on vector quarkonia decay branching fraction measurements
• Experimental review of the ${\rm Y}(1S,2S,3S)$ physics at $e^{+}{e}^{-}$ colliders and the LHC
• Search for light tetraquark states in ${\rm Y}(1S)$ and ${\rm Y}(2S)$ decays
• Test of QCD at large $Q^2$ with exclusive hadronic processes