Observation of the Isospin-Violating Decay J/ψ → φπ⁰ f₀(980)


Using a sample of 1.31 x 10⁹ J/ψ events collected with the BESIII detector at the BEPCII collider, the decays J/ψ → φπ⁺π⁻π⁰ and J/ψ → φπ⁰π⁰π⁰ are investigated. The isospin-violating decay J/ψ → φπ⁰f₀(980) with f₀(980) → ππ is observed for the first time. The width of the f₀(980) obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the π⁰f₀(980) mass spectrum, there is evidence of f₁(1285) production. By studying the decay J/ψ → φη', the branching fractions of η' → π⁺π⁻π⁰ and η' →π⁰π⁰π⁰, as well as their ratio, are also measured.

Causality (Physics), Branching fractions (Nuclear physics), Kaons, Mass (Physics), Radioactive decay, Particle tracks (Nuclear physics), Photons
This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contracts No. 11125525, No. 11235011, No. 11322544, No. 11335008, and No. 11425524; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. 11179007, No. U1232201, and No. U1332201; CAS under Contracts No. KJCX2-YW-N29 and No. KJCX2-YW-N45; German Research Foundation DFG under Collaborative Research Center Contract No. CRC-1044; Ministry of Development of Turkey under Contract No. DPT2006K-120470; Russian Foundation for Basic Research under Contract No. 14-07-91152; U.S. Department of Energy under Contracts No. DE-FG02-04ER41291, No. DE-FG02-05ER41374, No. DE-FG02-94ER40823, and No. DESC0010118; and WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.
©2015 American Physical Society