Thursday, July 08, 2010

New Measurement Shrinks The Size of Proton

The big news this week is the recently published paper in Nature[1] of the new size of the proton. Using a muonic hydrogen atom (a hydrogen atom where the electron has been replaced by a muon), a new Lamb shift measurement has produced a result of the size of a proton from 0.877 fm to 0.8418 fm.

Big deal, you say. But the implication of this can be quite astounding. The previous measurement was done based on the Lamb shift of a regular hydrogen atom. So the discrepancy (taking into account that the muon is heavier than the electron, etc.) may have a more profound effect, such as either the calculation is at fault, or that there may be a problem with QED itself.

There certainly could be hints of new physics here.


[1] R. Pohl et al., Nature v.466, p.213 (2010)

1 comment:

Anonyme said...

This is really some cool shit. I haven't heard anything more recent from this and am very interested if there are any new developments in the story.

Theoretically this experiment is supposed to be very well understood. We did the necessary calculations for the state of the particle in an undergrad QM course and it is relatively easy to understand. So how is this discrepancy in measurement going to be resolved?

I think that this really suggests that some of the postulates of QM are incorrect. I have a tendency to want Einstein to be correct that the mathematics of QM is really a consequence of some approximate statistics and not a fundamental theory of physics. I have a really hard time believing that at a fundamental level all of physics can be described by a simple linear theory that is postulated by QM!

Are there other reasonable interpretations of this result that do not violate postulates of QM?