There’s been a lot of reporting recently on a puzzle in particle physics that I haven’t previously written about. There have been two attempts, a preliminary one in 2010 and a more detailed one reported just this month, to measure the size of a proton by studying the properties of an exotic atom, called “muonic hydrogen”. Similar to hydrogen, which consists of a proton orbited by an electron (Figure 1), this atom consists of a proton and a short-lived heavy cousin of the electron, called the muon (Figure 2). A muon, as far as we have ever been able to tell, is just like an electron in all respects except that it is heavier; more precisely, the electromagnetic force and the strong and weak nuclear force treat electrons and muons in exactly the same way. Only the first two of these forces should play a role in atoms (and neither gravity nor any force due to the Higgs field should matter either). So because we have confirmed our understanding of ordinary hydrogen with very high precision, we believe we also understand muonic hydrogen very well also. But something’s amiss. Continue reading
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- Completed Final Section of Article on Dark Matter and LHC
- Science Festival About to Start in Cambridge, MA
- More on Dark Matter and the Large Hadron Collider
- Dark Matter: How Could the Large Hadron Collider Discover It?
- The LHC restarts — in a manner of speaking —
- How Evidence for Cosmic Inflation Was Reduced to Dust
- Giving Public Talk Jan. 20th in Cambridge, MA
- How a Trigger Can Potentially Make or Break an LHC Discovery