“…(5) can be compared with b η ¼ 0.428ð89Þ from CELLO [32] and b η ¼ 0.501ð38Þ from CLEO [33]. The TFF was also measured in the timelike region with the results b η ¼ 0.57ð12Þ from Lepton-G [46], b η ¼ 0.585ð51Þ from NA60 [47], b η ¼ 0.58ð11Þ from A2 [48], and b η ¼ 0.68ð26Þ from WASA [49]. Recently, the A2 Collaboration reported b η ¼ 0.59ð5Þ [50], the most precise experimental extraction up to date.…”
Section: η and η 0 Transition Form Factors At Low And Intermediatmentioning
The η and η 0 transition form factors in the spacelike region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. The slope and curvature parameters of the form factors as well as their values at zero and infinity are extracted from experimental data. The impact of these results on the mixing parameters of the η-η 0 system and the pseudoscalar-exchange contributions to the hadronic light-by-light scattering part of the anomalous magnetic moment a μ are also discussed.
“…(5) can be compared with b η ¼ 0.428ð89Þ from CELLO [32] and b η ¼ 0.501ð38Þ from CLEO [33]. The TFF was also measured in the timelike region with the results b η ¼ 0.57ð12Þ from Lepton-G [46], b η ¼ 0.585ð51Þ from NA60 [47], b η ¼ 0.58ð11Þ from A2 [48], and b η ¼ 0.68ð26Þ from WASA [49]. Recently, the A2 Collaboration reported b η ¼ 0.59ð5Þ [50], the most precise experimental extraction up to date.…”
Section: η and η 0 Transition Form Factors At Low And Intermediatmentioning
The η and η 0 transition form factors in the spacelike region are analyzed at low and intermediate energies in a model-independent way through the use of rational approximants. The slope and curvature parameters of the form factors as well as their values at zero and infinity are extracted from experimental data. The impact of these results on the mixing parameters of the η-η 0 system and the pseudoscalar-exchange contributions to the hadronic light-by-light scattering part of the anomalous magnetic moment a μ are also discussed.
“…Depending on the mass m M of the decaying meson, the leptons l can be either e ± or µ ± . Figure 11: Slope parameter of the timelike η transition form factor from Dalitz decays [54,55,56,57]. The gray band shows the current average value and its uncertainty listed by the PDG [4].…”
In view of the current 3 -4 σ deviation between theoretical and experimental values for the muon's anomalous magnetic moment, we review the ongoing efforts in constraining the hadronic light-by-light contribution to a µ by using dispersive techniques combined with a dedicated experimental program to obtain the required hadronic input.
“…An improved value of BR(η/η → γγ) or constructing a different ratio, as we do below, can allow sensitivity to these corrections. Results for the form factors F η/η γ * γ * (Q 2 ) can be broadly classified into three groups: theoretical predictions [53][54][55][56], experimental extractions [57][58][59][61][62][63], and dispersion analyses [64][65][66][67]. The standard parameterization for f (z) is a series expansion in z…”
Rare meson decay experiments promise to measure branching ratios as small as 10 −13 . This presents an opportunity to discover the µ + µ − bound state true muonium. We consider a set of possible channels, all with branching ratios above ∼ 10 −11 . For the electromagnetic decays η/η → (µ + µ − )γ, theoretical and phenomenological form factors F η/η γγ * (Q 2 ) allow predictions of BR(η → (µ + µ − )γ) ∼ 4.8 × 10 −10 and BR(η → (µ + µ − )γ) ∼ 3.7 × 10 −11 at the 5% level. Discussion of experimental prospects and potential backgrounds are made.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.