Welcome to a Scintilla of Playful Musings

Welcome to my new blog, noos anakainisis, translated literally as mind renewal. The primary obsessions are neuroscience, computation, information, structure, form, art and history of science. Some environmental, political, and technological developments will also be included.

I hope your neurons are sufficiently stimulated...

Wednesday, July 7, 2010

QED called into question by new calculation of the size of a hydrogen proton

The root-mean-square charge radius, rp, has been determined with an accuracy of 2 per cent (at best) by electron–proton scattering experiments. The present most accurate value of rp (with an uncertainty of 1 per cent) is given by the CODATA compilation of physical constants. This value is based mainly on precision spectroscopy of atomic hydrogen and calculations of bound-state quantum electrodynamics (QED).  However, using an exotic version of hydrogen (muonic hydrogen in which a proton is orbited by a negative muon) and pulsed laser spectroscopy to measure the muonic Lamb shift, the value of rp is 5 standard deviations off of previous value.  This implies either that the Rydberg constant has to be shifted by −110 kHz/c (4.9 standard deviations), or the calculations of the QED effects in atomic hydrogen or muonic hydrogen atoms are insufficient.

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Tristan said...

I need to educate myself as to what constitutes 'radius' in the setting of a particle described by a wave function.

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