Pion transition form factor from twisted-mass lattice QCD and the hadronic light-by-light ${\ensuremath{\pi}}^{0}$-pole contribution to the muon $g\ensuremath{-}2$

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Pion transition form factor from twisted-mass lattice QCD and the hadronic light-by-light $π^{0}$ -pole contribution to the muon $g - 2$

C. Alexandrou, S. Bacchio, G. Bergner, S. Burri, J. Finkenrath, A. Gasbarro, K. Hadjiyiannakou, K. Jansen, G. Kanwar, B. Kostrzewa, G. Koutsou, K. Ottnad, M. Petschlies, F. Pittler, F. Steffens, C. Urbach, and U. Wenger (Extended Twisted Mass Collaboration)

Phys. Rev. D 108, 094514 – Published 28 November 2023

Abstract

The neutral pion generates the leading pole contribution to the hadronic light-by-light tensor, which is given in terms of the nonperturbative transition form factor $F_{π^{0} γ γ} (q_{1}^{2}, q_{2}^{2})$ . Here we present an ab-initio lattice calculation of this quantity in the continuum and at the physical point using twisted-mass lattice QCD. We report our results for the transition form factor parametrized using a model-independent conformal expansion valid for arbitrary spacelike kinematics and compare it with experimental measurements of the single-virtual form factor, the two-photon decay width, and the slope parameter. We then use the transition form factors to compute the pion-pole contribution to the hadronic light-by-light scattering in the muon $g - 2$ , finding $a_{μ}^{π^{0} - pole} = 56.7 (3.2) \times 10^{- 11}$ .

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Received 1 September 2023
Accepted 6 October 2023

DOI:https://doi.org/10.1103/PhysRevD.108.094514

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society

Physics Subject Headings (PhySH)

Lattice field theory Magnetic moment

Pions

Form factors

Ab initio calculations Lattice QCD Path-integral Monte Carlo

Particles & Fields

Authors & Affiliations

C. Alexandrou^1,2, S. Bacchio², G. Bergner³, S. Burri⁴, J. Finkenrath^5,2, A. Gasbarro⁴, K. Hadjiyiannakou^1,2, K. Jansen⁶, G. Kanwar⁴, B. Kostrzewa⁷, G. Koutsou², K. Ottnad⁸, M. Petschlies^9,10, F. Pittler², F. Steffens^9,10, C. Urbach^9,10, and U. Wenger ⁴ (Extended Twisted Mass Collaboration)

¹Department of Physics, University of Cyprus, 20537 Nicosia, Cyprus
²Computation-based Science and Technology Research Center, The Cyprus Institute, 20 Konstantinou Kavafi Street, 2121 Nicosia, Cyprus
³University of Jena, Institute for Theoretical Physics, Max-Wien-Platz 1, D-07743 Jena, Germany
⁴Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, CH–3012 Bern, Switzerland
⁵Bergische Universität Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany
⁶Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, 15738 Zeuthen, Germany
⁷High Performance Computing and Analytics Lab, Rheinische Friedrich-Wilhelms-Universität Bonn, Friedrich-Hirzebruch-Allee 8, D-53115 Bonn, Germany
⁸PRISMA+ Cluster of Excellence and Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, Johann-Joachim-Becher-Weg 45, D-55128 Mainz, Germany
⁹HISKP (Theory), Rheinische Friedrich-Wilhelms-Universität Bonn, Nussallee 14-16, D-53115 Bonn, Germany
¹⁰Bethe Center for Theoretical Physics, Rheinische Friedrich-Wilhelms-Universität Bonn, Wegelerstraße 10, D-53115 Bonn, Germany

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Vol. 108, Iss. 9 — 1 November 2023

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Physical Review D

covering particles, fields, gravitation, and cosmology

Pion transition form factor from twisted-mass lattice QCD and the hadronic light-by-light $π^{0}$ -pole contribution to the muon $g - 2$

C. Alexandrou, S. Bacchio, G. Bergner, S. Burri, J. Finkenrath, A. Gasbarro, K. Hadjiyiannakou, K. Jansen, G. Kanwar, B. Kostrzewa, G. Koutsou, K. Ottnad, M. Petschlies, F. Pittler, F. Steffens, C. Urbach, and U. Wenger (Extended Twisted Mass Collaboration)

Phys. Rev. D 108, 094514 – Published 28 November 2023

Abstract

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Article Text

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Issue

Physical Review D

covering particles, fields, gravitation, and cosmology

Pion transition form factor from twisted-mass lattice QCD and the hadronic light-by-light π0-pole contribution to the muon g−2

C. Alexandrou, S. Bacchio, G. Bergner, S. Burri, J. Finkenrath, A. Gasbarro, K. Hadjiyiannakou, K. Jansen, G. Kanwar, B. Kostrzewa, G. Koutsou, K. Ottnad, M. Petschlies, F. Pittler, F. Steffens, C. Urbach, and U. Wenger (Extended Twisted Mass Collaboration)

Phys. Rev. D 108, 094514 – Published 28 November 2023

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Pion transition form factor from twisted-mass lattice QCD and the hadronic light-by-light $π^{0}$ -pole contribution to the muon $g - 2$