Robust Limit on a Varying Proton-to-Electron Mass Ratio from a Single H2 System

The variation of the dimensionless fundamental physical constant mu = m(p)/m(e) can be checked through observation of Lyman and Werner lines of molecular hydrogen in the spectra of distant QSOs. Only few systems have been used for the purpose providing different results between the different authors. Our intention is to resolve the current controversy on variation of mu and devise explanations for the different findings. An analysis based on independent data sets of QSO 0347-383 is put forward and new approaches for some of the steps involved in the data analysis are introduced. Drawing on two independent observations of a single absorption system in QSO 0347-383 our detailed analysis yields Delta mu/mu = (15 +/- (9(stat) + 6(sys))) x 10(-6) at Z(abs) = 3.025. Current analyses tend to underestimate the impact of systematic errors. This work presents alternative approaches to handle systematics and introduces methods required for precision analysis of QSO spectra available in the near future.