Indication of a Cosmological Variation of the Proton-Electron Mass Ratio Based on Laboratory Measurement and Reanalysis of H2 Spectra
Based on highly accurate laboratory measurements of Lyman bands of H2 and an updated representation of the structure of the ground XΣg+1 and excited BΣu+1 and CΠu1 states, a new set of sensitivity coefficients Ki is derived for all lines in the H2 spectrum, representing the dependence of their transition wavelengths on a possible variation of the proton-electron mass ratio μ=mp/me. Included are local perturbation effects between B and C levels and adiabatic corrections. The new wavelengths and Ki factors are used to compare with a recent set of highly accurate H2 spectral lines observed in the Q 0347-383 and Q 0405-443 quasars, yielding a fractional change in the mass ratio of Δμ/μ=(2.4±0.6)×10-5 for a weighted fit and Δμ/μ=(2.0±0.6)×10-5 for an unweighted fit. This result indicates, at a 3.5σ confidence level, that μ could have decreased in the past 12 Gyr.