Observation of the decay J/Ψ → e+e-η(1405) with η(1405) →†’ π0f0(980)

• Using a data sample of (10087 ± 44) x 106 J/ψ events collected by the BESIII detector in 2009, 2012, 2018 and 2019, the electromagnetic Dalitz process J/ψ → e+e-η(1405) is observed via the decay η(1405) → π0f0(980), f0(980) → π+π-, with a significance of about 9.8σ. The branching fraction of this decay is measured to be B(J/ψ → e+e−η(1405) → e+e−π0f0(980) → J/ψ→ e+e-η(1405) → e+e-π0f0(980) → e+e-π0π+ π-) = (2.04 ± 0.20(stat) ± 0.08(syst)) x 10-7. The branching fraction ratio B(J/ψ → e+e- η(1405))/B(J/ψ → γη(1405)) is determined to be (1.36 ± 0.17(stat) ± 0.06(syst)) x 10-2. Furthermore, an e+e- invariant mass dependent transition form factor of J/ψ → e+e-η(1405) is presented for the first time. The obtained result provides input for different theoretical models and is valuable for the improved understanding the intrinsic structure of the η(1405) meson.

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NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

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