New limit on possible variation of the proton-to-electron mass ratio

A.V. Ivanchik1, E. Rodriguez2, P. Petitjean2,3, D.A. Varshalovich1
1Ioffe Physical Technical Institute RAS, St.-Petersburg, Russia
2Institut d'Astrophysique de Paris - CNRS, France
3LERMA - Observatoire de Paris, France

We estimate the cosmological variation of the proton-to-electron mass ratio \mu by measuring the wavelengths of molecular hydrogen transitions in the early Universe. The analysis is performed using high spectral resolution observations (FWHM\approx 7 km/s) of two damped Lyman-alpha systems at zabs=2.3377 and 3.0249 observed along the lines of sight to the quasars Q 1232+082 and Q 0347-382 respectively.

The most conservative result of the analysis is a possible variation of \mu over the last ~ 10 Gyrs, with an amplitude

Delta \mu / \mu = (5.7\pm3.8)\times 10-5.
The result is significant at the 1.5-sigma level only and should be confirmed by further observations. This is the most stringent estimate of a possible cosmological variation of \mu obtained up to now.
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