First constraint on cosmological variation of the proton-to-electron
  mass ratio from two independent telescopes
  A high signal-to-noise spectrum covering the largest number of hydrogen lines
(90 H2 lines and 6 HD lines) in a high redshift object was analyzed from an
observation along the sight-line to the bright quasar source J2123$-$005 with
the UVES spectrograph on the ESO Very Large Telescope (Paranal, Chile). This
delivers a constraint on a possible variation of the proton-to-electron mass
ratio of Dmu/mu = (8.5 \pm 3.6_{stat} \pm 2.2_{syst}) x 10^{-6} at redshift
z=2.059$, which agrees well with a recently published result on the same system
observed at the Keck telescope yielding Dmu/mu = (5.6 \pm 5.5_{stat} \pm
2.9_{syst}) x 10^{-6}. Both analyses used the same robust absorption line
fitting procedures with detailed consideration of systematic errors.
