Search for Cosmological µ-Variation from High-Redshift H2 Absorption A Status Report

Observations of H2 spectra in the line-of-sight of distant quasars may reveal a variation of the proton-electron mass ratio μ = m _p ∕ m _e at high redshift, typically for z > 2. Currently four high-quality systems (Q0347-383, Q0405-443, Q0528-250 and J2123-050) have been analyzed returning a constraint Δμ ∕ μ < 1 ×10^− 5. We present data and a μ-variation analysis of another system, Q2348–011 at redshift z _abs  = 2. 42, delivering Δμ ∕ μ = ( − 1. 5 ± 1. 6) ×10 ^− 5. In addition to observational data the status of the laboratory measurements is reviewed. The future possibilities of deriving a competitive constraint on Δμ ∕ μ from the known high-redshift H₂ absorbers is investigated, resulting in the identification of a number of potentially useful systems for detecting μ-variation.