Dispersive analysis of the Primakoff reaction $$\gamma K \rightarrow K \pi $$

Dax, Maximilian; Stamen, Dominik; Kubis, Bastian

doi:10.1140/epjc/s10052-021-08951-x

“…As pointed out in Ref. [ 77 ], the latter constitutes one of the dominant uncertainties in an analysis of the reaction , where a value deduced from a VMD analysis of kaon form factors in a wider (timelike) energy range [ 71 ] was employed, corresponding to . From our analysis, we conclude that the inclusion of spacelike data does not reduce the uncertainty in this coupling constant appreciably, cf.…”

Section: Fits To Datamentioning

confidence: 99%

Kaon electromagnetic form factors in dispersion theory

Stamen¹,

Hariharan²,

Hoferichter

³

et al. 2022

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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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“…As pointed out in Ref. [77], the latter constitutes one of the dominant uncertainties in an analysis of the reaction γK → Kπ, where a value deduced from a VMD analysis of kaon form factors in a wider (timelike) energy range [71] was employed, corresponding to c ω = 1.29 (15). From our analysis, we…”

Section: Fits To Datamentioning

confidence: 99%

Kaon electromagnetic form factors in dispersion theory

Stamen,

Hariharan,

Hoferichter

et al. 2022

Preprint

Self Cite

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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“…Similar dispersive analyses have also been carried out for πN [124,149,150,[155][156][157], γ ( * ) γ ( * ) → ππ [158][159][160][161][162], e + e − → π + π − [163], γπ → ππ [164,165] and γK → πK [166]. The approach for obtaining rigorous and precise poles from dispersively constrained data fits, is also well-suited for the recent lattice calculations that we hope may shed further light on these issues.…”

Section: Cfd I=1 P-wavementioning

confidence: 83%

Precision dispersive approaches versus unitarized chiral perturbation theory for the lightest scalar resonances $$\sigma /f_0(500) $$ and $$\kappa /K_0^*(700) $$

Peláez

¹

,

Rodas

²

,

Elvira

³

2021

Eur. Phys. J. Spec. Top.

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For several decades, the σ/f0(500) and κ/K * 0 (700) resonances have been subject to long-standing debate. Both their existence and properties were controversial until very recently. In this tutorial review we compare model-independent dispersive and analytic techniques versus unitarized Chiral Perturbation Theory, when applied to the lightest scalar mesons σ/f0(500) and κ/K * 0 (700). Generically, the former have settled the long-standing controversy about the existence of these states, providing a precise determination of their parameters, whereas unitarization of chiral effective theories allows us to understand their nature, spectroscopic classification and dependence on QCD parameters. Here we review in a pedagogical way their uses, advantages and caveats.

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Dispersive analysis of the Primakoff reaction $$\gamma K \rightarrow K \pi $$

Cited by 10 publications

References 78 publications

Kaon electromagnetic form factors in dispersion theory

Kaon electromagnetic form factors in dispersion theory

Kaon electromagnetic form factors in dispersion theory

Precision dispersive approaches versus unitarized chiral perturbation theory for the lightest scalar resonances $$\sigma /f_0(500) $$ and $$\kappa /K_0^*(700) $$

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