Hadronic light-by-light contribution to the muon g — 2

Adolfo Guevara

doi:10.1088/1742-6596/761/1/012009

Abstract

We have computed the hadronic light-by-light (LbL) contribution to the muon anomalous magnetic moment aμ in the frame of Chiral Perturbation Theory with the inclusion of the lightest resonance multiplets as dynamical fields (RχT). It is essential to give a more accurate prediction of this hadronic contribution due to the future projects of J-Parc and FNAL on reducing the uncertainty in this observable. We, therefore, computed the pseudoscalar transition form factor and proposed the measurement of the e+ e- →μ+ μ- π0 cross section and dimuon invariant mass spectrum to determine more accurately its parameters. Then, we evaluated the pion exchange contribution to αμ, obtaining (6.66 ± 0.21) • 10-10. By comparing the pion exchange contribution and the pion-pole approximation to the corresponding transition form factor (πTFF) we recalled that the latter underestimates the complete πTFF by (15-20)%. Then, we obtained the η(') TFF, obtaining a total contribution of the lightest pseudoscalar exchanges of (10.47 ± 0.54) • 10-10, in agreement with previous results and with smaller error.

Highlights

Ever since the measurement of the electron magnetic moment in the splitting of the ground states of deuterium and molecular hydrogen [1], the anomalous magnetic moment has been an ever more stringent test of the underlying theory governing the interactions among elemental particles; giving us the lead from a way of renormalizing QED [2] to an outstanding confirmation of QFT with QED contributions [3] up to order α πIn this spirit, the aμ has been seen as a very stringent test of beyond standard model physics (BSM)
By comparing the pion exchange contribution and the pion-pole approximation to the corresponding transition form factor we recalled that the latter underestimates the complete πTFF by (15-20)%
Within the Standard Model (SM), the contributions to the aμ that have a greater uncertainty are the hadronic ones [5]. This is due to the fact that the underlying theory cannot be taken perturbatively in the whole energy range of the quark loop integrals, forcing theorists to compute these contributions using effective field theories (EFT) based on symmetries of Quantum Chromodynamics (QCD)

Summary

Introduction

Ever since the measurement of the electron magnetic moment in the splitting of the ground states of deuterium and molecular hydrogen [1], the anomalous magnetic moment has been an ever more stringent test of the underlying theory governing the interactions among elemental particles; giving us the lead from a way of renormalizing QED [2] to an outstanding confirmation of QFT with QED contributions [3] up to order α πIn this spirit, the aμ has been seen as a very stringent test of beyond standard model physics (BSM). We have computed the hadronic light-by-light (LbL) contribution to the muon anomalous magnetic moment aμ in the frame of Chiral Perturbation Theory with the inclusion of the lightest resonance multiplets as dynamical fields (RχT).

Results

Conclusion