Towards an improved understanding of $$\varvec{\eta \rightarrow \gamma ^*\gamma ^*}$$

Holz, S.; Plenter, Judith; Xiao, C. W.; Dato, T.; Hanhart, C.; Kubis, Bastian; Meißner, Ulf‐G.; Wirzba, A.

doi:10.1140/epjc/s10052-021-09661-0

Cited by 21 publications

(11 citation statements)

References 79 publications

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“…First, we turn to the HLbL contribution [ 34 , 35 , 105 , 122 – 134 , 146 – 150 ] in which case the uncertainty is dominated by subleading contributions beyond pseudoscalar poles and two-meson cuts, see Refs. [ 47 , 151 – 159 ] for recent work in this direction. Meanwhile, states prove to be appreciably suppressed compared to their analog, which is true for both the leading box contributions (estimated in VMD [ 34 ] or DS equations [ 35 , 36 ]) and rescattering corrections [ 157 ], in the latter case despite the strong coupling between the and channels via the .…”

Section: Applicationsmentioning

confidence: 99%

Kaon electromagnetic form factors in dispersion theory

Stamen¹,

Hariharan²,

Hoferichter

et al. 2022

Eur. Phys. J. C

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The electromagnetic form factors of charged and neutral kaons are strongly constrained by their low-energy singularities, in the isovector part from two-pion intermediate states and in the isoscalar contribution in terms of $$\omega $$ ω and $$\phi $$ ϕ residues. The former can be predicted using the respective $$\pi \pi \rightarrow {{\bar{K}}} K$$ π π → K ¯ K partial-wave amplitude and the pion electromagnetic form factor, while the latter parameters need to be determined from electromagnetic reactions involving kaons. We present a global analysis of time- and spacelike data that implements all of these constraints. The results enable manifold applications: kaon charge radii, elastic contributions to the kaon electromagnetic self energies and corrections to Dashen’s theorem, kaon boxes in hadronic light-by-light (HLbL) scattering, and the $$\phi $$ ϕ region in hadronic vacuum polarization (HVP). Our main results are: $$\langle r^2\rangle _\text {c}=0.359(3)\,\text {fm}^2$$ ⟨ r 2 ⟩ c = 0.359 ( 3 ) fm 2 , $$\langle r^2\rangle _\text {n}=-0.060(4)\,\text {fm}^2$$ ⟨ r 2 ⟩ n = - 0.060 ( 4 ) fm 2 for the charged and neutral radii, $$\epsilon =0.63(40)$$ ϵ = 0.63 ( 40 ) for the elastic contribution to the violation of Dashen’s theorem, $$a_\mu ^{K\text {-box}}=-0.48(1)\times 10^{-11}$$ a μ K -box = - 0.48 ( 1 ) × 10 - 11 for the charged kaon box in HLbL scattering, and $$a_\mu ^\text {HVP}[K^+K^-, \le 1.05\,\text {GeV}]=184.5(2.0)\times 10^{-11}$$ a μ HVP [ K + K - , ≤ 1.05 GeV ] = 184.5 ( 2.0 ) × 10 - 11 , $$a_\mu ^\text {HVP}[K_SK_L, \le 1.05\,\text {GeV}]=118.3(1.5)\times 10^{-11}$$ a μ HVP [ K S K L , ≤ 1.05 GeV ] = 118.3 ( 1.5 ) × 10 - 11 for the HVP integrals around the $$\phi $$ ϕ resonance. The global fit to $${{\bar{K}}} K$$ K ¯ K gives $${{\bar{M}}}_\phi =1019.479(5)\,\text {MeV}$$ M ¯ ϕ = 1019.479 ( 5 ) MeV , $${\bar{ \varGamma }}_\phi =4.207(8)\,\text {MeV}$$ Γ ¯ ϕ = 4.207 ( 8 ) MeV for the $$\phi $$ ϕ resonance parameters including vacuum-polarization effects.

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Section: Applicationsmentioning

confidence: 99%

Kaon electromagnetic form factors in dispersion theory

Stamen¹,

Hariharan²,

Hoferichter

et al. 2022

Eur. Phys. J. C

Self Cite

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show abstract

“…in which case the uncertainty is dominated by subleading contributions beyond pseudoscalar poles and two-meson cuts, see Refs. [47,[151][152][153][154][155][156][157][158][159] for recent work in this direction. Meanwhile, KK states prove to be appreciably suppressed compared to their ππ analog, which is true for both the leading box contributions (estimated in VMD [34] or DS equations [35,36]) and rescattering corrections [157], in the latter case despite the strong coupling between the ππ and KK channels via the f 0 (980).…”

Section: Kaon-box Contribution To Hlbl Scatteringmentioning

confidence: 99%

Kaon electromagnetic form factors in dispersion theory

Stamen,

Hariharan,

Hoferichter

et al. 2022

Preprint

View full text Add to dashboard Cite

The electromagnetic form factors of charged and neutral kaons are strongly constrained by their lowenergy singularities, in the isovector part from twopion intermediate states and in the isoscalar contribution in terms of ω and φ residues. The former can be predicted using the respective ππ → KK partialwave amplitude and the pion electromagnetic form factor, while the latter parameters need to be determined from electromagnetic reactions involving kaons. We present a global analysis of time-and spacelike data that implements all of these constraints. The results enable manifold applications: kaon charge radii, elastic contributions to the kaon electromagnetic self energies and corrections to Dashen's theorem, kaon boxes in hadronic light-by-light (HLbL) scattering, and the φ region in hadronic vacuum polarization (HVP). Our main results are: r 2 c = 0.359(3) fm 2 , r 2 n = −0.060(4) fm 2 for the charged and neutral radii, = 0.63( 40) for the elastic contribution to the violation of Dashen's theorem, a K-box µ = −0.48(1) × 10 −11 for the charged kaon box in HLbL scattering, and a HVP µ [K + K − , ≤ 1.05 GeV] = 184.5(2.0) × 10 −11 , a HVP µ [K S K L , ≤ 1.05 GeV] = 118.3(1.5) × 10 −11 for the HVP integrals around the φ resonance. The global fit to KK gives Mφ = 1019.479(5) MeV, Γφ = 4.207(8) MeV for the φ resonance parameters including vacuumpolarization effects.

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“…and lattice QCD [37]. In this part of the evaluation, ongoing work thus mainly concerns a consolidation of the η, η poles, both using dispersion relations [176,177] and lattice QCD [178,179] (see Refs. [155,180] for recent work on the box contributions).…”

Section: Contributionmentioning

confidence: 99%

Prospects for precise predictions of $a_μ$ in the Standard Model

Colangelo,

Davier,

El-Khadra

et al. 2022

Preprint

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Towards an improved understanding of $$\varvec{\eta \rightarrow \gamma ^\gamma ^}$$

Abstract: We argue that high-quality data on the reaction $$e^+e^-\rightarrow \pi ^+\pi ^-\eta $$ e + e - → π + π - η … Show more

Cited by 21 publications

References 79 publications

Kaon electromagnetic form factors in dispersion theory

Kaon electromagnetic form factors in dispersion theory

Kaon electromagnetic form factors in dispersion theory

Prospects for precise predictions of $a_μ$ in the Standard Model

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