Constraint on a varying proton-to-electron mass ratio from molecular hydrogen absorption toward quasar SDSS J123714.60+064759.5

TL;DR

This study used molecular hydrogen absorption lines in a distant quasar to test if the proton-to-electron mass ratio has changed over 11.4 billion years, finding no significant variation.

Contribution

First precise measurement of proton-to-electron mass ratio variation using H2 absorption in a high-redshift quasar with detailed systematic correction.

Findings

No significant variation in mu detected within uncertainties.

Systematic effects from wavelength calibration were carefully corrected.

Constraints are consistent with a constant mu over 11.4 billion years.

Abstract

Molecular hydrogen transitions in the sub-damped Lyman alpha absorber at redshift z = 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 H2 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 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 dmu/mu = (-5.4 \pm 6.3 stat \pm 4.0 syst) x 10^(-6), consistent with no variation over a look-back time of 11.4 Gyrs.