Indication of a cosmological variation of the proton-electron mass ratio based on laboratory measurement and reanalysis of H-2 spectra
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Based on highly accurate laboratory measurements of Lyman bands of H-2 and an updated representation of the structure of the ground X (1)Sigma(+)(g) and excited B (1)Sigma(+)(u) and C (1)Pi(u) states, a new set of sensitivity coefficients K-i is derived for all lines in the H-2 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 H-2 spectral lines observed in the Q 0347-383 and Q 0405-443 quasars, yielding a fractional change in the mass ratio of Delta mu/mu=(2.4 +/- 0.6)x10(-5) for a weighted fit and Delta mu/mu=(2.0 +/- 0.6)x10(-5) for an unweighted fit. This result indicates, at a 3.5 sigma confidence level, that mu could have decreased in the past 12 Gyr.