Two photon couplings of the lightest isoscalars from BELLE data

We analyse within the framework of resonance chiral theory the SA µ A ν and SV µ V ν three-point Green functions, where S, A µ and V µ are short for scalar, axial-vector and vector SU (3) hadronic currents. We construct the necessary Lagrangian such that the Green functions fulfill the asymptotic constraints, at large momenta, imposed by QCD at leading order. We study the implications of our results on the spectrum of scalars in the large-N C limit, and analyse their decays. *

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“…(B.1) the amplitudes M SP 1 P 2 are given in the following subsections. Those for the decays of the S L multiplet are: [53,54].…”

Section: B S → P P Decay Amplitudesmentioning

confidence: 99%

“…For the phase-shifts we will only need δ I=0 ππ (M 2 f i ) and δ I=0 KK (M 2 f i ), because in two-body decays always s = M 2 being M the mass of the decaying particle. The phase shifts are given by the extended K-matrix fit following [53,54], up to 1.8 GeV. We will consider the results in Table C.1.…”

mentioning

confidence: 99%

Scalar-involved three-point Green functions and their phenomenology

2019

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“…The normalization of the transverse form factors is computed from the experimentally measured two-photons widths [37], Γ γγ = Γ (0) γγ + Γ (2) γγ , assuming that the ratio of helicity 2 to helicity 0 decays is r = 91.3 % (see Ref. [62]):…”

Section: Tensor Mesonsmentioning

confidence: 99%

Hadronic light-by-light scattering amplitudes from lattice QCD versus dispersive sum rules

et al. 2018

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The hadronic contribution to the eight forward amplitudes of light-by-light scattering (γ * γ * → γ * γ * ) is computed in lattice QCD. Via dispersive sum rules, the amplitudes are compared to a model of the γ * γ * → hadrons cross sections in which the fusion process is described by hadronic resonances. Our results thus provide an important test for the model estimates of hadronic light-by-light scattering in the anomalous magnetic moment of the muon, a HLbL µ . Using simple parametrizations of the resonance M → γ * γ * transition form factors, we determine the corresponding monopole and dipole masses by performing a global fit to all eight amplitudes. Together with a previous dedicated calculation of the π 0 → γ * γ * transition form factor, our calculation provides valuable information for phenomenological estimates of a HLbL µ . The presented calculations are performed in two-flavor QCD with pion masses extending down to 190 MeV at two different lattice spacings. In addition to the fully connected Wick contractions, on two lattice ensembles we also compute the (2+2) disconnected class of diagrams, and find that their overall size is compatible with a parameter-free, large-N inspired prediction, where N is the number of colors. Motivated by this observation, we estimate in the same way the disconnected contribution to a HLbL µ . arXiv:1712.00421v1 [hep-lat] 1 Dec 2017 2 Contents

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“…The factor R defined from Eqs. (9)(10)(11) is an "estimate" of the factor, by which the listed cross-sections Σ need to be scaled to give the contribution of each channel and energy region to the PV sumrule -see text for the discussion.…”

Section: Contributions To the Sumrules: Single Particle And ππ Kkmentioning

confidence: 99%

Pascalutsa-Vanderhaeghen light-by-light sum rule from photon-photon collisions

Dai¹,

Pennington²

2017

Phys. Rev. D

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Light-by-light scattering sumrules based on general field theory principles relate crosssections with different helicities. In this paper the simplest sumrule is tested for the I = 0 and 2 channels for "real" photon-photon collisions. Important contributions come from the longlived pseudoscalar mesons and from di-meson intermediate states. The latest Amplitude Analysis of γγ → ππ, KK allows this contribution to be evaluated. However, we find that other multi-meson contributions up to 2.5 GeV are required to satisfy the sumrules. While data on three and four pion cross-sections exist, there is no information about their isospin and helicity decomposition. Nevertheless, we show the measured cross-sections are sufficiently large to ensure the sumrules for the helicity differences are likely fulfilled.

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Two photon couplings of the lightest isoscalars from BELLE data

Cited by 50 publications

References 79 publications

Scalar-involved three-point Green functions and their phenomenology

Scalar-involved three-point Green functions and their phenomenology

Hadronic light-by-light scattering amplitudes from lattice QCD versus dispersive sum rules

Pascalutsa-Vanderhaeghen light-by-light sum rule from photon-photon collisions

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