g−2 of charged leptons, α(MZ2) , and the hyperfine splitting of muonium

Abstract

Following updates in the compilation of e þ e − → hadrons data, this work presents reevaluations of the hadronic vacuum polarization contributions to the anomalous magnetic moments of the electron (a e), muon (a μ) and tau lepton (a τ), to the ground-state hyperfine splitting of muonium and also updates the hadronic contributions to the running of the QED coupling at the mass scale of the Z boson, αðM 2 Z Þ. Combining the results for the hadronic vacuum polarization contributions with recent updates for the hadronic light-bylight corrections, the electromagnetic and the weak contributions, the deviation between the measured value of a μ and its Standard Model prediction amounts to Δa μ ¼ ð28.02 AE 7.37Þ × 10 −10 , corresponding to a muon g − 2 discrepancy of 3.8σ.

Consistency of hadronic vacuum polarization between lattice QCD and the R ratio

“…The established theory result for the muon anomalous magnetic moment, a µ , exhibits a 3.3σ [1] to a 3.8σ [2] tension with the results of the BNL experiment [3]. Within this year, we expect the Fermilab g − 2 experiment [4] to release first results towards their target to reduce the uncertainties of the BNL experiment by a factor of 4.…”

Muon g − 2 vs LHC Run 2 in supersymmetric models

“…These values correspond to 3.8 and 3.3 σ level discrepancies, respectively: ∆a µ ≡ a exp µ − a SM µ = (27.8 ± 7.4) × 10 −10 [7], (26.1 ± 7.9) × 10 −10 [8].…”

“…where g µ is the magnetic moment of the muon. The Standard Model (SM) value is composed of the QED [1,2], electroweak [3][4][5][6], hadronic vacuum polarization [7,8], and hadronic light-by-light [9,10] contributions. #1 The latest results are a SM µ = (11 659 181.08 ± 3.78) × 10 −10 [7], (11 659 183.0 ± 4.8) × 10 −10…”

Light gauge boson interpretation for (g − 2)μ and the KL→ π0 + (invisible) anomaly at the J-PARC KOTO experiment

“…Recently, intriguing explanations of KOTO event excess with the models including light scalars coupled to quarks [11][12][13], light dark sector fermions [14], and generic higher dimensional operators in the neutrino sector [15] have been suggested. The long-lasting (g − 2) µ discrepancy at the level of (3.3 − 4.1)σ between observations [16][17][18][19] and SM predictions [20][21][22][23][24][25][26][27] strongly implies the presence of new physics 1 . Various new physics explaining (g − 2) µ has been suggested so far, and the U (1) Lµ−Lτ gauge boson X [29][30][31][32] with its mass in the range 10 MeV ∼ < m X ∼ < 200 MeV is still preferred after taking the present experimental observations [33].…”

“…their result eliminates the need to invoke new physics to explain the discrepancy between SM prediction and experimental measurement. In our work, we have considered the 3.8σ muon g-2 discrepancy, based on recently updated results by KNT2019[27].…”