Muon g-2 and a Geocentric New Field.

Light scalars can in principle couple to both bulk matter and fermion spin, with hierarchically disparate strengths. Storage ring measurements of fermion electromagnetic moments via spin precession can be sensitive to such a force, sourced by Earth. We discuss how this force could lead to the current deviation of the measured muon anomalous magnetic moment, g-2, from the standard model prediction. Due to its different parameters, the proposed J-PARC muon g-2 experiment can provide a direct test of our hypothesis. A future search for the proton electric dipole moment can have good sensitivity for the coupling of the assumed scalar to nucleon spin. We also argue that supernova constraints on the axion-muon coupling may not be applicable in our framework.

Is the θ[over ¯] Parameter of QCD Constant?

Testing the cosmological variation of fundamental constants of nature can provide valuable insights into new physics scenarios. While many such constraints have been derived for standard model coupling constants and masses, the θ[over ¯] parameter of QCD has not been as extensively examined. In this Letter, we discuss potentially promising paths to investigate the time dependence of the θ[over ¯] parameter. While laboratory searches for CP-violating signals of θ[over ¯] yield the most robust bounds on today's value of θ[over ¯], we show that CP-conserving effects provide constraints on the variation of θ[over ¯] over cosmological timescales. We find no evidence for a variation of θ[over ¯] that could have implied an "iron-deficient" Universe at higher redshifts. By converting recent atomic clock constraints on a variation of constants, we infer d(θ[over ¯]^{2})/dt≤6×10^{-15} yr^{-1}, at 1σ. Finally, we also sketch an axion model that results in a varying θ[over ¯] and could lead to excess diffuse gamma ray background, from decays of axions produced in high redshift supernova explosions.

Two-Loop Binding Corrections to the Electron Gyromagnetic Factor.

We compute corrections to the gyromagnetic factor of an electron bound in a hydrogenlike ion at order α^{2}(Zα)^{5}. This result removes a major uncertainty in predictions for silicon and carbon ions, used to determine the atomic mass of the electron.

Enhanced Electromagnetic Corrections to the Rare Decay B_{s,d}→µ

We investigate electromagnetic corrections to the rare B-meson leptonic decay B_{s,d}→µ^{+}µ^{-} from scales below the bottom-quark mass m_{b}. Contrary to QCD effects, which are entirely contained in the B-meson decay constant, we find that virtual photon exchange can probe the B-meson structure, resulting in a "nonlocal annihilation" effect. We find that this effect gives rise to a dynamical enhancement by a power of m_{b}/Λ_{QCD} and by large logarithms. The impact of this novel effect on the branching ratio of B_{s,d}→µ^{+}µ^{-} is about 1%, of the order of the previously estimated nonparametric theoretical uncertainty, and four times the size of previous estimates of next-to-leading order QED effects due to residual scale dependence. We update the standard model (SM) prediction to B[over ¯](B_{s}→µ^{+}µ^{-})_{SM}=(3.57±0.17)×10^{-9}.