# Analysis of carbon monoxied absorption at z=2.5 to constrain variation of the proton-to-electron mass ratio

## TL;DR

This study uses quasar absorption spectra to place constraints on the possible variation of the proton-to-electron mass ratio over 11 billion years, finding no significant change.

## Contribution

It presents a new measurement of mu variation at z=2.5 using CO absorption lines with improved calibration techniques.

## Key findings

- No significant variation of mu detected within uncertainties
- Constraints improve previous limits on mu variation at high redshift
- Spectral modeling confirms consistency with constant mu over 11.2 Gyrs

## Abstract

Absorption by carbon monoxide in the spectrum of quasar SDSS J000015.16+004833.2 is investigated in order to derive a constraint on the temporal variation of the proton-to-electron mass ratio, mu. The spectrum was recorded using VLT/UVES, and it was partially corrected for long-range wavelength scale distortions using the supercalibration technique. Eight vibrational CO singlet-singlet bands belonging to the A-X electronic absorption system, and the perturbing d3-X(5, 0) singlet-triplet band are detected in the damped Lyman-alpha system at z =2.52. The spectra are modelled using a comprehensive fitting technique, resulting in a final value of Dmu/mu=(1.8 +/- 2.2 +/- 0.4)x10e(-5), which is consistent with no variation over a look-back time of 11.2 Gyrs.