Thursday, April 20, 2006

Inconstant Muon

Ok, here's something...

Rheinold et al Phys Rev Lett 151101, v96 (2006) claim a lab measurement showing that μ = mp/me has changed over time.

They compare measurements of UV spectra of molecular hydrogen in the lab sensitive to the electron/proton mass ratio with redshifted measurements of the same transition (so observed in the optical in the local rest frame), and conclude with 3.5σ confidence that there has been a 20 part per million change in the effective mass ratio.

Well, I believe the lab measurements. The QSO observations were done with UVES on the VLT and are of redshift ~ 2-3 quasars.
Hm, they are measuring absolute wavelengths, so the simplest explanation is that the narrow H2 lines are systematically offset from the lines used to determine the redshift of the complex doing the absorbing - not intrinsically silly, depending on how close they are and what is being measured, haven't tracked down the VLT paper.

File this under "something to keep an eye on", but be skeptical.


Anonymous Anonymous said...

It's good pun, but after reading your heading I kept looking for how they were measuring the muon mass.

Maybe it's an aftereffect of the anesthesia.

Anyhow, put me down as extremely skeptical. There's a history of such claims, as you know.

2:05 PM  
Blogger Steinn said...

Er, if m_e/m_p is inconstant, than m_\mu ought to vary with respect to at least one of them...
Sorry, couldn't resist.

Yeah, I'm skeptical too, but I'm in a "be nice to alternative theories" mood right now for obscure reasons.

I blame open minded grad students meself.

2:13 PM  
Blogger Leucipo said...

The key work about the electron proton mass quotient is of course

Friedrich Lenz "The Ratio of Proton and Electron Masses" Phys. Rev. 82, 554 (1951)

I quoted this and other related works in the thread

4:19 AM  

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