New constraint on cosmological variation of the proton-to-electron mass ratio from Q0528-250

Molecular hydrogen transitions in quasar spectra can be used to constrain variation in the proton-to-electron mass ratio, mu= m(p)/m(e), at high redshifts (z greater than or similar to 2). We present here an analysis of a new spectrum of the quasar Q0528-250, obtained on Very Large Telescope (VLT)/Ultraviolet and Visual Echelle Spectrograph (UVES), and analyse the well-known H2 absorber at z = 2.811 in this spectrum. For the first time we detect deuterated molecular hydrogen (HD) in this system with a column density of log10(N/cm(-2)) = 13.27 +/- 0.07; HD is sensitive to variation in mu, and so we include it in our analysis. Using 76 H2 and seven HD transitions we constrain variation in mu from the current laboratory value to be mu/mu= (0.3 +/- 3.2stat +/- 1.9sys) x 10-6, which is consistent with no cosmological variation in mu, as well as with previous results from other H2/HD absorbers. The main sources of systematic uncertainty relate to accurate wavelength calibration of the spectra and the re-dispersion of multiple telescope exposures on to the one pixel grid.