Towards a data-driven analysis of hadronic light-by-light scattering

Colangelo, Gilberto; Hoferichter, Martin; Kubis, Bastian; Procura, Massimiliano; Stoffer, Peter

doi:10.1016/j.physletb.2014.09.021

Cited by 204 publications

(178 citation statements)

References 80 publications

(115 reference statements)

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“…[702] for an overview. There are ongoing efforts in lattice QCD [703] and dispersive approaches [704,705] to provide model-independent information on the magnitude of the HLbL contribution. , τ , η−, or t, σ, ω.…”

Section: Applicationsmentioning

confidence: 99%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

406

530

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We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon processes and Compton scattering determined in the DysonSchwinger framework with those of lattice QCD and the available experimental data. The general aim is to identify the underlying physical mechanisms behind the plethora of observable phenomena in terms of the underlying quark and gluon degrees of freedom.

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Section: Applicationsmentioning

confidence: 99%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

406

530

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“…given by the two-pion contribution to the unitarity relation for the HLbL tensor: 29) where W µν are the matrix elements for γ * γ * → ππ. The subscripts {+−, 00} denote the charges and p 1,2 the momenta of the intermediate pions.…”

Section: Jhep04(2017)161mentioning

confidence: 99%

“…Current estimates for HLbL scattering in (g − 2) µ are largely based on hadronic models [16][17][18][19][20][21][22][23][24][25][26][27], which despite implementing different limits of QCD, such as large-N c , chiral symmetry, or constraints from perturbative QCD, all involve a certain amount of uncontrollable uncertainties without offering a systematic path forward. In order to improve the determination of the HLbL contribution, we proposed a dispersive framework [28], based on the fundamental principles of analyticity, unitarity, gauge invariance, and crossing symmetry, which opens up a path towards a data-driven evaluation [29]. As the next step [30,31], we presented a comprehensive solution to the task of constructing a basis for the HLbL tensor devoid of kinematic singularities, defining scalar functions that are amenable to a dispersive treatment.…”

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.

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362

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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“…Other approaches that combine phenomenological constraints with information from lattice QCD employ expansions of a hvp µ in terms of Mellin-Barnes moments [10][11][12] or finite energy sum rules [13,14]. The hadronic light-by-light scattering contribution has so far only been determined via model estimates (as reviewed in [5,[15][16][17]), although efforts have been undertaken to move towards a data-driven [18][19][20][21][22][23][24][25][26][27] approach as well.…”

Section: Jhep10(2017)020mentioning

confidence: 99%

The hadronic vacuum polarization contribution to the muon g − 2 from lattice QCD

Morte

Francis

Gülpers

et al. 2017

J. High Energ. Phys.

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We present a calculation of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment, a hvp µ , in lattice QCD employing dynamical up and down quarks. We focus on controlling the infrared regime of the vacuum polarization function. To this end we employ several complementary approaches, including Padé fits, time moments and the time-momentum representation. We correct our results for finitevolume effects by combining the Gounaris-Sakurai parameterization of the timelike pion form factor with the Lüscher formalism. On a subset of our ensembles we have derived an upper bound on the magnitude of quark-disconnected diagrams and found that they decrease the estimate for a hvp JHEP10 (2017)020 10 −10 , where the first error is statistical, and the second denotes the combined systematic uncertainty. Based on our findings we discuss the prospects for determining a hvp µ with sub-percent precision.

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Towards a data-driven analysis of hadronic light-by-light scattering

Cited by 204 publications

References 80 publications

Baryons as relativistic three-quark bound states

Baryons as relativistic three-quark bound states

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

The hadronic vacuum polarization contribution to the muon g − 2 from lattice QCD

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