Observation of the isospin-violating decayJ/ψ→ϕπ0f0(980

Abstract

Observation of the isospin-violating decay J/ψ→ϕπ^{0}f_{0}(980) Observation of the isospin-violating decay J/ψ → φπ 0 f 0 (980) Using a sample of 1.31 billion J/ψ events collected with the BESIII detector at the BEPCII collider, the decays J/ψ → φπ + π − π 0 and J/ψ → φπ 0 π 0 π 0 are investigated. The isospin violating decay J/ψ → φπ 0 f0(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 π 0 f0(980) mass spectrum, there is evidence of f1(1285) production. By studying the decay J/ψ → φη ′ , the branching fractions of η ′ → π + π − π 0 and η ′ → π 0 π 0 π 0 , as well as their ratio, are 3 also measured.M

Theoretical description of the J/ψ→η(η′)hWu1, Sakai2, Oset3 2019Phys. Rev. D11190View full textAdd to dashboardCite

“…It is interesting to note that this decay mode was later confirmed by experiment in Ref. [32], in agreement with the strength and the narrow shape predicted in Ref. [27].…”

Study of the isospin breaking decay Y(2175)→ϕf0(980)Cheng1, Li2, Wang3 et al. 2019Phys. Rev. D8030View full textAdd to dashboardCite

“…Because of the narrow peak near the KK thresholds in the ηπ 0 invariant mass spectrum, the event selection criteria for the a 0 0 (980) candidates has high efficiency. In addition, the final states contain six photons and two charged tracks, the detection efficiency for J/ψ → ηY (2175)) → ηφf 0 (980) → ηφηπ 0 decay can be as large as 8% after the final selection [37,42,52,53]. The BESIII experiment will accumulate huge data sample of 10 × 10 9 J/ψ decays by the end of 2019 [53][54][55].…”

Isospin violations at BESIII

“…The scalar meson f 0 (980), which is explained as a tetraquark [1,2], a KK molecule [3], or a quark-antiquark gluon hybrid [4] in theory, is found with a width of ∼ 10 MeV in isospin violating processes [5,6,7], which is much narrower than that of ∼ 50 MeV in the isospin conservation decays [8]. The significant excess of J/ψ → γη(1405) → γπ 0 f 0 (980) with the anomalously large isospin violation was observed at BESIII [5].…”

“…Another theory, which is thought to be a feasible approach to clarify the phenomenon of the narrower f 0 (980), is the mixing mechanism of a 0 0 (980) − f 0 (980) [10,11]. The BESIII collaboration recently observed the a 0 0 (980) − f 0 (980) mixing with the statistical significance in excess of 5.0 standard deviations (σ ) [7].…”

“…In theory, a model of triangle singularity Feynman diagram was proposed to reconcile the anomaly [9]. In 2015, another J/ψ → V π 0 f 0 (980) measurement was observed at BESIII [6], where the vector particle V is the ϕ meson. Similarly, the observed f 0 (980) is narrower (about 15 MeV in width) than the world average in the same year [8].…”