Citation:
Date Published:
October 1, 2009Abstract:
In an effort to resolve the discrepancy between two measurements of thefundamental constant μ, the proton to electron mass ratio, at earlytimes in the universe we reanalyze the same data used in the earlierstudies. Our analysis of the molecular hydrogen absorption lines inarchival Very Large Telescope/Ultraviolet and Visible EchelleSpectrometer (UVES) spectra of the damped Lyman alpha systems in thequasi-stellar objects Q0347-383 and Q0405-443 yields a combinedmeasurement of a Δμ/μ value of (-7 ± 8) ×10-6, consistent with no change in the value of μ over atime span of 11.5 Gyr. Here, we define Δμ as (μ z - μ0) where μ z is the value of μat a redshift of z and μ0 is the present-day value. Ournull result is consistent with the recent measurements of King et al.,Δμ/μ = (2.6 ± 3.0) × 10-6, andinconsistent with the positive detection of a change in μ by Reinholdet al. Both of the previous studies and this study are based on the samedata but with differing analysis methods. Improvements in the wavelengthcalibration over the UVES pipeline calibration is a key element in bothof the null results. This leads to the conclusion that the fundamentalconstant μ is unchanged to an accuracy of 10-5 over the