Indication of a Cosmological Variation of the Proton-Electron Mass Ratio Based on Laboratory Measurement and Reanalysis ofH2Spectra

Abstract

Based on highly accurate laboratory measurements of Lyman bands of H2 and an updated representation of the structure of the ground X 1sigma(g)+ and excited B 1sigma(u)+ and C 1pi(u) states, a new set of sensitivity coefficients K(i) 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 mu = m(p)/m(e). Included are local perturbation effects between B and C levels and adiabatic corrections. The new wavelengths and K(i) 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 deltamu/mu = (2.4 +/- 0.6) x 10(-5) for a weighted fit and deltamu/mu = (2.0 +/- 0.6) x 10(-5) for an unweighted fit. This result indicates, at a 3.5sigma confidence level, that mu could have decreased in the past 12 Gyr.