Dispersive analysis of the γγ⁎ → ππ process

Danilkin, Igor; Vanderhaeghen, Marc

doi:10.1016/j.physletb.2018.12.047

Cited by 57 publications

(98 citation statements)

References 51 publications

(59 reference statements)

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“…Once a suitable set of Lorentz structures is found, the rest is straightforward. Our work is a continuation of a previous work where, for the first time, the single virtual case for the d-wave has been studied [17]. In the double virtual photon case, there is an additional complication related to the anomalous threshold behavior as it was pointed out in [18].…”

Section: Introductionmentioning

confidence: 66%

“…In [17] the kinematically unconstrained basis of the partial wave amplitudes were derived for the single virtual case. Below we extend this result for the double-virtual case for J = 2,…”

Section: Kinematic Constraintsmentioning

confidence: 99%

“…The dominant contribution is generated by vector mesons ω and ρ. The contribution from other heavier resonances will be absorbed in an effective way by allowing for a slight adjustment of the V Pγ coupling [17].…”

Section: Dispersion Relationsmentioning

confidence: 99%

“…where in the following we will use g V Pγ C ρ ±,0 π ±,0 γ C ωπ 0 γ /3 as the only fit parameter, as discussed in [17], yielding g V Pγ = 0.33 GeV −1 . This value lies within 10% with the PDG average g PDG V Pγ = 0.37(2) [4], thus justifying the approximation of left-hand cuts by vector mesons.…”

Section: Left-hand Cutsmentioning

confidence: 99%

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Dispersive analysis of the γγ→ππ process

2020

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In this paper, we present a dispersive analysis of the double-virtual photon-photon scattering to two pions up to 1.5 GeV. Through unitarity, this process is very sensitive to hadronic final state interaction. For the s-wave, we use a coupled-channel ππ, KK analysis which allows a simultaneous description of both f 0 (500) and f 0 (980) resonances. For higher energies, f 2 (1270) shows up as a dominant structure which we approximate by a single channel ππ rescattering in the d-wave. In the dispersive approach, the latter requires taking into account t-and u-channel vector-meson exchange left-hand cuts which exhibit an anomalous-like behavior for large space-like virtualities. In our paper, we show how to readily incorporate such behavior using a contour deformation. Besides, we devote special attention to kinematic constraints of helicity amplitudes and show their correlations explicitly.

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Section: Introductionmentioning

confidence: 66%

“…In [17] the kinematically unconstrained basis of the partial wave amplitudes were derived for the single virtual case. Below we extend this result for the double-virtual case for J = 2,…”

Section: Kinematic Constraintsmentioning

confidence: 99%

Section: Dispersion Relationsmentioning

confidence: 99%

Section: Left-hand Cutsmentioning

confidence: 99%

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Dispersive analysis of the γγ→ππ process

2020

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“…(6.15). This way of proceeding allows a clear splitting between the RHC and LHC contributions, which is also exploited in the literature [172,186,187,188]. A DR for L(s) along the LHC is typically written,…”

Section: The Omnès Solutionmentioning

confidence: 99%

Coupled-channel approach in hadron–hadron scattering

Oller

2020

Progress in Particle and Nuclear Physics

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Coupled-channel dynamics for scattering and production processes in partial-wave amplitudes is discussed from a perspective that emphasizes unitarity and analyticity. We elaborate on several methods that have driven to important results in hadron physics, either by themselves or in conjunction with effective field theory. We also develop and compare with the use of the Lippmann-Schwinger equation in near-threshold scattering. The final(initial)-state interactions are discussed in detail for the elastic and coupled-channel case. Emphasis has been put in the derivation and discussion of the methods presented, with some applications examined as important examples of their usage.

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Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

Colangelo

Hagelstein

Hoferichter

et al. 2020

J. High Energ. Phys.

278

164

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While the low-energy part of the hadronic light-by-light (HLbL) tensor can be constrained from data using dispersion relations, for a full evaluation of its contribution to the anomalous magnetic moment of the muon (g − 2) µ also mixed-and high-energy regions need to be estimated. Both can be addressed within the operator product expansion (OPE), either for configurations where all photon virtualities become large or one of them remains finite. Imposing such short-distance constraints (SDCs) on the HLbL tensor is thus a major aspect of a model-independent approach towards HLbL scattering. Here, we focus on longitudinal SDCs, which concern the amplitudes containing the pseudoscalar-pole contributions from π 0 , η, η . Since these conditions cannot be fulfilled by a finite number of pseudoscalar poles, we consider a tower of excited pseudoscalars, constraining their masses and transition form factors from Regge theory, the OPE, and phenomenology. Implementing a matching of the resulting expressions for the HLbL tensor onto the perturbative QCD quark loop, we are able to further constrain our calculation and significantly reduce its model dependence. We find that especially for the π 0 the corresponding increase of the HLbL contribution is much smaller than previous prescriptions in the literature would imply. Overall, we estimate that longitudinal SDCs increase the HLbL contribution by ∆a LSDC µ = 13(6) × 10 −11 . A Anomalous Pseudoscalar-Vector-Vector Coupling 46 B Alternative model for pion, η, and η transition form factors 48 1 Introduction Current Standard Model (SM) evaluations of the anomalous magnetic moment of the muon, a µ = (g − 2) µ /2, differ from the value measured at the Brookhaven National Laboratory [1]a exp µ = 116 592 089(63) × 10 −11 , (1.1) by around 3.5 σ. In the near future, the new Fermilab E989 experiment [2] will be able to reduce the experimental uncertainty by a factor 4, and the E34 experiment at J-PARC [3] will provide an important cross check, see ref.[4] for a comparison of the experimental methods. Therefore, the theoretical calculation of a µ needs to be improved accordingly. The uncertainty of the SM prediction mainly stems from hadronic contributions, such as hadronic vacuum polarization (HVP), see figure 1 (a), and HLbL scattering, see figure 1 (b). Since the HVP contribution can be systematically calculated with a data-driven dispersive approach [5-9], lattice QCD [10][11][12][13][14][15][16], and potentially be accessed independently by the proposed MUonE experiment [17,18], which aims to measure the space-like finestructure constant α(t) in elastic electron-muon scattering, the HLbL contribution may end up dominating the theoretical error. 1 Apart from lattice QCD [27][28][29], recent data-driven approaches towards HLbL scattering are again rooted in dispersion theory, either for the HLbL tensor [30][31][32][33][34][35], the Pauli 1 Note that higher-order insertions of HVP [5,19,20] and HLbL [21] are already under sufficient control, as are hadronic corrections in the anomalou...

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Dispersive analysis of the γγ⁎ → ππ process

Cited by 57 publications

References 51 publications

Dispersive analysis of the γγ→ππ process

Dispersive analysis of the γγ→ππ process

Coupled-channel approach in hadron–hadron scattering

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

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Dispersive analysis of the γγ⁎ → ππ process

Cited by 57 publications

References 51 publications

Dispersive analysis of the γ*γ*→ππ process

Dispersive analysis of the γ*γ*→ππ process

Coupled-channel approach in hadron–hadron scattering

Longitudinal short-distance constraints for the hadronic light-by-light contribution to (g − 2)μ with large-Nc Regge models

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Product

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Dispersive analysis of the γγ⁎ → ππ process

Dispersive analysis of the γγ→ππ process

Dispersive analysis of the γγ→ππ process