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Physicists Finally Nail the Proton's Size, and Hope Dies Quanta Magazine

#artificialintelligence

In 2010, physicists in Germany reported that they had made an exceptionally precise measurement of the size of the proton, the positively charged building block of atomic nuclei. The result was very puzzling. Randolf Pohl of the Max Planck Institute of Quantum Optics and collaborators had measured the proton using special hydrogen atoms in which the electron that normally orbits the proton was replaced by a muon, a particle that's identical to the electron but 207 times heavier. Pohl's team found the muon-orbited protons to be 0.84 femtometers in radius -- 4% smaller than those in regular hydrogen, according to the average of more than two dozen earlier measurements. If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons -- a fundamental discovery.


Physicists Finally Nail the Proton's Size, and Hope Dies Quanta Magazine

#artificialintelligence

In 2010, physicists in Germany reported that they had made an exceptionally precise measurement of the size of the proton, the positively charged building block of atomic nuclei. The result was very puzzling. Randolf Pohl of the Max Planck Institute of Quantum Optics and collaborators had measured the proton using special hydrogen atoms in which the electron that normally orbits the proton was replaced by a muon, a particle that's identical to the electron but 207 times heavier. Pohl's team found the muon-orbited protons to be 0.84 femtometers in radius -- 4% smaller than those in regular hydrogen, according to the average of more than two dozen earlier measurements. If the discrepancy was real, meaning protons really shrink in the presence of muons, this would imply unknown physical interactions between protons and muons -- a fundamental discovery.


The proton radius revisited

Science

The nucleus of all atoms consists of protons and neutrons, and the simplest of all atoms, hydrogen, has just one proton. The radius of the proton is very small, about 1 fm (1 fm is 10 15 m), smaller than the radius of a hydrogen atom by a factor of 60,000. As a proton is such a fundamental particle, much effort is devoted to measuring its size. Since 2010, proton size has been puzzling theorists and experimentalists alike. Measuring transition frequencies in an exotic form of hydrogen, where instead of an electron a muon--an elementary particle 200 times heavier than the electron--is orbiting the proton, a 4% smaller proton size was found (1).


Physicists Are Closer to Knowing the Size of a Proton … Sort of

WIRED

How big is a proton? That might sound like a pretty simple question, but it turned out to have the potential to wreck a lot of modern physics. That's because different methods of measuring the proton's charge radius produced results that disagreed--and not just by a little bit. The answers were four standard deviations apart. But now, a new and improved measurement brings them into much closer alignment--though not quite close enough that we can consider the issue resolved. This story originally appeared on Ars Technica, a trusted source for technology news, tech policy analysis, reviews, and more.


How big is a proton? We may finally have the answer to this puzzle

New Scientist

We aren't quite sure what the radius of a proton is and a new way of measuring has helped to fix the puzzle. Until 2010, we were fairly sure about the size of the proton. We had measured it using hydrogen atoms, which are made of one proton and one electron.