Dispersion relations for hadronic light-by-light scattering in triangle kinematics

Feb 23, 2023
38 pages
Published in:
  • JHEP 04 (2023) 125,
  • JHEP 04 (2023) 125
  • Published: Apr 26, 2023
e-Print:
Report number:
  • PSI-PR-23-5,
  • UWThPh 2023-5,
  • ZU-TH 10/23

Citations per year

2020202120222023202410914
Abstract: (Springer)
We present a new strategy for the dispersive evaluation of the hadronic light-by-light contribution to the anomalous magnetic moment of the muon aμ_{μ}. The new approach directly applies in the kinematic limit relevant for aμ_{μ}: one of the photons is treated as an external electromagnetic field with vanishing momentum, so that the kinematics corresponds to a triangle. We derive expressions for the relevant single-particle intermediate states, as well as the tensor decompositions of the two-pion sub-processes that appear in addition to those needed in the established dispersive approach. The existing approach is based on a set of dispersion relations for the hadronic light-by-light tensor in four-point kinematics. At present it is not known how to consistently include in this framework resonant intermediate states of spin 2 or larger, due to the appearance of kinematic singularities that can be traced back to the redundancy of the tensor decomposition. We show that our new approach circumvents this problem and enables dispersion relations in the limit of triangle kinematics that are manifestly free from kinematic singularities, paving the way towards a data-driven evaluation of all relevant exclusive hadronic intermediate states.
Note:
  • 38 pages, 4 figures, 1 table; extended discussion of crossing symmetry, version published in JHEP
  • Chiral Lagrangian
  • Nonperturbative Effects
  • Effective Field Theories
  • Precision QED
  • photon photon: scattering
  • muon: magnetic moment
  • spin: 2
  • kinematics
  • dispersion relation
  • intermediate state