<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>ω</mml:mi><mml:mo>→</mml:mo><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:msup><mml:mi>γ</mml:mi><mml:mo>*</mml:mo></mml:msup></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>ϕ</mml:mi><mml:mo>→</mml:mo><mml:msup><mml:mi>π</mml:mi><mml:mn>0</mml:mn></mml:msup><mml:msup><mml:mi>γ</mml:mi><mml:mo>*</mml:mo></mml:msup></mml:math>transition form factors in dispersion

Schneider, S.; Kubis, Bastian; Niecknig, Franz

doi:10.1103/physrevd.86.054013

Cited by 125 publications

(183 citation statements)

References 34 publications

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“…In both Equation 8 and Equation 9, Λ is the mass and width of the virtual vector meson, while γ is the width of the virtual vector meson. Recent measurements of the transition form factor for ω → μ + μ − π 0 have shown unexpected discrepancies with the Vector Dominance Model [8] and recent models of chiral Lagrangian field theory [9], and dispersion theory [10] attempt to predict the contributions of the virtual vector meson, as seen in Fig. 2.…”

Section: The Transition Form Factor Of the ω Mesonmentioning

confidence: 99%

“…Shown are VMD (dotted line) Eqs. (6, 9) using the mass of the ρ meson as the virtual vector meson, the results of a chiral Lagrangian treatment with explicit vector mesons [9] (white shaded curve with solid borders), a simplified approximation to the full dispersive solution [10] (gray shaded curve with dashed borders), full dispersive solution [10] (black hatched curve with solid borders). [10] …”

Section: The Transition Form Factor Of the ω Mesonmentioning

confidence: 99%

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Light meson decays from photon-induced reactions with CLAS

Kunkel

2016

EPJ Web Conf.

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Abstract. Photoproduction experiments with the CEBAF Large Acceptance Spectrometer CLAS at the Thomas Jefferson National Facility produce data sets with competitive statistics of light mesons. With these data sets, measurements of transition form factors for η, ω, and η mesons via conversion decays can be performed using the invariant mass distribution of the final state dileptons. Tests of fundamental symmetries and information on the light quark mass difference can be performed using a Dalitz plot analysis of the meson decay. An overview of preliminary results, from existing CLAS data, and future prospects within the newly upgraded CLAS12 apparatus are given.

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Section: The Transition Form Factor Of the ω Mesonmentioning

confidence: 99%

Section: The Transition Form Factor Of the ω Mesonmentioning

confidence: 99%

Light meson decays from photon-induced reactions with CLAS

Kunkel

2016

EPJ Web Conf.

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“…This representation ensures that the form factor behaves as 1/s asymptotically as long as the phase shift approaches π, up to logarithms in agreement with the expectation from perturbative QCD [95][96][97][98][99]. We impose this asymptotic behavior by smoothly extrapolating δ 1 1 to π from the boundary s m of the applicability of the Roy solution, but checked that introducing effects from ρ , ρ excitations as suggested in [40] does not impact the space-like form factor. The form of G inel can be further constrained by requiring that the imaginary part exhibit the expected P -wave behavior and respect the Eidelman-Lukaszuk bound [100], but again the impact on the space-like form factor proves to be small.…”

Section: Jhep04(2017)161mentioning

confidence: 99%

“…In this framework, we worked out how to define unambiguously and in a model-independent way both the pion-pole and the pion-box contribution. 1 With pion-as well as η-, η -pole contributions determined by their doubly-virtual transition form factors, which by themselves are strongly constrained by unitarity, analyticity, and perturbative QCD in combination with experimental data [38][39][40][41][42][43][44][45][46], we here apply our framework to extend the partial-wave formulation of two-pion rescattering effects for S-waves [28] to arbitrary partial waves. To this end, we identify a special set of (unambiguously defined) scalar functions that fulfill unsubtracted dispersion relations and can be expressed as linear combinations of helicity amplitudes.…”

Section: Introductionmentioning

confidence: 99%

Dispersion relation for hadronic light-by-light scattering: two-pion contributions

Colangelo

Hoferichter

Procura

et al. 2017

J. High Energ. Phys.

371

257

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In this third paper of a series dedicated to a dispersive treatment of the hadronic light-by-light (HLbL) tensor, we derive a partial-wave formulation for two-pion intermediate states in the HLbL contribution to the anomalous magnetic moment of the muon (g − 2) µ , including a detailed discussion of the unitarity relation for arbitrary partial waves. We show that obtaining a final expression free from unphysical helicity partial waves is a subtle issue, which we thoroughly clarify. As a by-product, we obtain a set of sum rules that could be used to constrain future calculations of γ * γ * → ππ. We validate the formalism extensively using the pion-box contribution, defined by two-pion intermediate states with a pion-pole left-hand cut, and demonstrate how the full known result is reproduced when resumming the partial waves. Using dispersive fits to high-statistics data for the pion vector form factor, we provide an evaluation of the full pion box, a π-box µ = −15.9(2)×10 −11 . As an application of the partial-wave formalism, we present a first calculation of ππ-rescattering effects in HLbL scattering, with γ * γ * → ππ helicity partial waves constructed dispersively using ππ phase shifts derived from the inverse-amplitude method. In this way, the isospin-0 part of our calculation can be interpreted as the contribution of the f 0 (500) to HLbL scattering in (g − 2) µ . We argue that the contribution due to charged-pion rescattering implements corrections related to the corresponding pion polarizability and show that these are moderate. Our final result for the sum of pion-box contribution and its S-wave rescattering corrections reads a π-box µ + a ππ,π-pole LHC µ,J=0 = −24(1) × 10 −11 .

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“…2(c), such that a vector-meson-dominance (VMD) approximation is justified here to a large extent. In the context of the π 0 , the corresponding ω → π 0 γ * and φ → π 0 γ * transition form factors have hence been treated dispersively [15][16][17] (see Ref. [18] for an extension even to the J/ψ → π 0 γ * transition), while a pure VMD description for F ss (q 2 1 , q 2 2 ) was so far deemed sufficient for the η (′) transition form factors.…”

Section: Definition Intermediate Statesmentioning

confidence: 99%

Towards a dispersive determination of the η and η′ transition form factors

Kubis¹

2018

EPJ Web Conf.

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Abstract.We discuss status and prospects of a dispersive analysis of the η and η ′ transition form factors. Particular focus is put on the various pieces of experimental information that serve as input to such a calculation. These can help improve on the precision of an evaluation of the η and η ′ pole contributions to hadronic light-by-light scattering in the anomalous magnetic moment of the muon. Hadronic light-by-light scattering and the anomalous magnetic moment of the muonThere is a by now long-standing discrepancy between the experimental determination of the anomalous magnetic moment of the muon as measured by the BNL E821 experiment [1], and its calculation within the Standard Model [2], with both experiment and theory affected by a comparable uncertainty. With two different proposals to further improve on the accuracy of the measurement well under way [3,4], it is of utmost importance to also improve the accuracy of the theoretical Standard-Model prediction before a persistent discrepancy of potentially increased significance can be interpreted in terms of physics beyond the Standard Model. The Standard-Model uncertainty is entirely dominated by hadronic contributions. While the dominant hadronic vacuum polarization can be expressed, via a dispersion relation, in terms of measurable e + e − → hadrons total cross sections, which therefore can be further improved upon by a strong experimental effort to determine many of the exclusive channels contributing therein with yet improved precision [5], the situation for the α QED -suppressed hadronic light-by-light scattering is less straightforward, relying until recently to a much larger extent on modeling [6], with badly controlled errors.This presentation is part of an effort to analyze also the hadronic light-by-light scattering tensor using dispersion theory [7,8]. Dispersion theory makes maximal use of analyticity and unitarity, two fundamental consequences of relativistic quantum field theories that mathematically incorporate the principles of causality and probability conservation. The various (in principle infinitely many different) contributions to hadronic light-by-light scattering are organized in terms of their analytic structure, according to the cuts and poles in the different energy variables that are dictated by the above principles. This has the advantage that all contributions will be given in terms of on-shell form factors and scattering amplitudes, hence observables that can to a large extent again be related to experimentally accessible quantities [9]. An ordering principle will be to consider intermediate

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ω→π0γandϕ→π0γtransition form factors in dispersion

Cited by 125 publications

References 34 publications

Light meson decays from photon-induced reactions with CLAS

Light meson decays from photon-induced reactions with CLAS

Dispersion relation for hadronic light-by-light scattering: two-pion contributions

Towards a dispersive determination of the η and η′ transition form factors

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ω→π0γ*andϕ→π0γ*transition form factors in dispersion

Cited by 125 publications

References 34 publications

Light meson decays from photon-induced reactions with CLAS

Light meson decays from photon-induced reactions with CLAS

Dispersion relation for hadronic light-by-light scattering: two-pion contributions

Towards a dispersive determination of the η and η′ transition form factors

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Product

Resources

About

ω→π0γandϕ→π0γtransition form factors in dispersion