Molecular hydrogen transitions in the sub-damped Lyman \alpha absorber at redshift z _ { \textrm { \scriptsize abs } } \simeq 2.69 , toward the background quasar SDSS J123714.60+064759.5 , were analyzed in order to search for a possible variation of the proton-to-electron mass ratio \mu over a cosmological time-scale .
The system is composed of three absorbing clouds where 137 H _ { 2 } and HD absorption features were detected .
The observations were taken with the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph with a signal-to-noise ratio of 32 per 2.5 km s ^ { -1 } pixel , covering the wavelengths from 356.6 to 409.5 nm .
A comprehensive fitting method was used to fit all the absorption features at once .
Systematic effects of distortions to the wavelength calibrations were analyzed in detail from measurements of asteroid and ‘ solar twin ’ spectra , and were corrected for .
The final constraint on the relative variation in \mu between the absorber and the current laboratory value is \Delta \mu / \mu = ( -5.4 \pm 6.3 _ { \textrm { \small { stat } } } \pm 4.0 _ { \textrm { \small { syst% } } } ) \times 10 ^ { -6 } , consistent with no variation over a look-back time of 11.4 Gyrs .