Precision Study of η′→γπ+π− Decay Dynamics

Abstract

Using a low background data sample of 9.7×10^{5} J/ψ→γη^{'}, η^{'}→γπ^{+}π^{-} events, which are 2 orders of magnitude larger than those from the previous experiments, recorded with the BESIII detector at BEPCII, the decay dynamics of η^{'}→γπ^{+}π^{-} are studied with both model-dependent and model-independent approaches. The contributions of ω and the ρ(770)-ω interference are observed for the first time in the decays η^{'}→γπ^{+}π^{-} in both approaches. Additionally, a contribution from the box anomaly or the ρ(1450) resonance is required in the model-dependent approach, while the process specific part of the decay amplitude is determined in the model-independent approach.

Search for the decay η′→γγη

“…The most stringent upper limit, reported by GAMS-4π setup, on the branching fraction of this decay is 8 × 10 −4 at the 90% confidence level (CL) [10]. The BESIII experiment using J=ψ radiative decays has observed a series of η 0 new decay modes [11][12][13][14][15][16][17], and in this paper we present a search for η 0 → γγη in the J=ψ radiative decay.…”

Experimental input for the HLbL contribution to themuon(g−2)

“…The precision experimental data on the radiative decays η ( ) → γ π + π − are used to predict the form factors in in the region relevant to η ( ) → γ e + e − [53,54,55]. The experimental input for η → γ π + π − is provided by WASA-at-COSY [56] and KLOE-2 [57] and for η → γ π + π − by BESIII [58]. To extend the predictions to other kinematic regions of the η and η TFFs, the data for other processes are needed e.g.…”

Measurement of B(J/ψ→η′e+e−Ablikim1, Ачасов2, Ahmed3 et al. 2019Phys. Rev. DSelf Cite17080View full textAdd to dashboardCite

“…The J=ψ to η 0 transition form factor is assumed to be a single-pole form jFðq 2 Þj ¼ 1=ð1 − q 2 =Λ 2 Þ, where q 2 is the fourmomentum transfer squared and Λ is the effective pole mass, with a value of Λ ¼ 3.686 GeV=c 2 . Then the subsequent decay mode of η 0 → γπ þ π − is simulated with the ρ-ω interference and box anomaly effects [35,36]. The decays of η 0 → π þ π − η and η → γγ are generated with a phase space model.…”