Observation of Upsilon(2S) -> eta Upsilon(1S) and search for related transitions

Abstract

We report the first observation of the transition Upsilon(2S) > eta Upsilon(1S), with branching fraction B=(2.1+0.7-0.6(stat.)+-0.3(syst.)) x 10^{-4} and statistical significance 5.3 sigma. Data were acquired with the CLEO detector at the CESR e+ e- symmetric collider. This is the first process observed involving a b-quark spin flip. Upper limits at 90% confidence level for related processes, in units of 10^{-4}, are B[Upsilon(2S) -> pi0 Upsilon(1S)] < 1.8, B[Upsilon(3S) -> eta Upsilon(1S)] < 1.8, B[Upsilon(3S) -> pi0 Upsilon(1S)] < 0.7, and B[Upsilon(3S) -> pi0 Upsilon(2S)] < 5.1.

9 pages, 2 figures, available through http://www.lns.cornell.edu/public/CLNS/, submitted to PRL. Revised systematic errors. Slightly shortened to conform to PRL line count

References in corpus (4)

• Big-Bang nucleosynthesis (Particle Data Group mini-review)
• Charmonium
• QCD Multipole Expansion and Hadronic Transitions in Heavy Quarkonium Systems
• Search for Radiative Decays of Upsilon(1S) into eta and eta'

Cited by in corpus (12)

• Observation of the ${\rm Y}(1^3{D}_J)$ Bottomonium State through Decays to ${\pi }^{+}{\pi }^{-}{\rm Y}(1S)$
• First observation of the hadronic transition ${\rm Y}(4S)\to \eta h_b(1P)$ and new measurement of the $h_b(1P)$ and ${\eta }_b(1S)$ parameters
• Recent Results in Bottomonium
• WIMPless Dark Matter and Meson Decays with Missing Energy
• Study of Upsilon(3S,2S) -> eta Upsilon(1S) and Upsilon(3S,2S) -> pi+pi- Upsilon(1S) hadronic trasitions
• Hadronic transitions from Upsilon(4S) as a probe of four-quark admixture
• The Pion-Photon Transition Form Factor and New Physics in the Tau Sector
• Measurements of branching fractions for electromagnetic transitions involving the ${\chi }_{bJ}(1P)$ states
• Improved Measurement of Branching Fractions for pipi Transitions among Upsilon(nS)States
• Study of the Hadronic Transitions ${\rm Y}$(2S)$\to (\eta ,{\pi }^0){\rm Y}$(1S) at Belle
• Experimental review of the ${\rm Y}(1S,2S,3S)$ physics at $e^{+}{e}^{-}$ colliders and the LHC
• Search for the decay $B_s^0\to J/\psi {\pi }^0$ at Belle experiment