Nearly all of science deals with baryonic matter and how the fundamental interactions affect such matter. Baryonic matter consists of quarks and particles made from quarks, like protons and neutrons. Free neutrons have a half life of 613.9 seconds. Electrons and protons appear to be stable, to the best of current knowledge. ;
The proton is the most important baryon, while the electron is the most important lepton;
The proton massmp is composed primarily of gluons, and of the quarks making up the proton. Hence mp, and therefore the ratioμ, are easily measurable consequences of the strong force. In fact, in the chiral limit, mp is proportional to the QCDenergy scale, ΛQCD. At a given energy scale, the strong coupling constantαs is related to the QCD scale as
Variation of ''μ'' over time
Astrophysicists have tried to find evidence that μ has changed over the history of the universe. One interesting cause of such change would be change over time in the strength of the strong force. Astronomical searches for time-varying μ have typically examined the Lyman series and Werner transitions of molecular hydrogen which, given a sufficiently largeredshift, occur in the optical region and so can be observed with ground-based spectrographs. If μ were to change, then the change in the wavelengthλi of each rest frame wavelength can be parameterised as: where Δμ/μ is the proportional change in μ and Ki is a constant which must be calculated within a theoretical framework. Reinhold et al. reported a potential 4 standard deviation variation in μ by analysing the molecular hydrogen absorption spectra of quasars Q0405-443 and Q0347-373. They found that. King et al. reanalysed the spectral data of Reinhold et al. and collected new data on another quasar, Q0528-250. They estimated that, different from the estimates of Reinhold et al.. Murphy et al. used the inversion transition of ammonia to conclude that at redshift. Kanekar used deeper observations of the inversion transitions of ammonia in the same system at towards 0218+357 to obtain. Bagdonaite et al. used methanol transitions in the spiral lens galaxy PKS 1830-211 to find at. Kanekar et al. used near-simultaneous observations of multiple methanol transitions in the same lens, to find at. Using three methanol lines with similar frequencies to reduce systematic effects, Kanekar et al. obtained. Note that any comparison between values of Δμ/μ at substantially different redshifts will need a particular model to govern the evolution of Δμ/μ. That is, results consistent with zero change at lower redshifts do not rule out significant change at higher redshifts.
