- #31
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Two different threads on the same topic have been merged.
Zz.
Zz.
QED Proton Size: 4% Smaller Than Thought?
Click For Summary
Discussion Overview
The discussion centers around the recent finding that the proton may be approximately 4% smaller than previously thought, which raises questions about the implications for Quantum Electrodynamics (QED) and related calculations, particularly the Lamb shift in hydrogen and muonic hydrogen. Participants explore potential experimental errors, theoretical implications, and the nature of proton size measurements.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
- Mathematical reasoning
Main Points Raised
- Some participants suggest that the discrepancy in proton size could be due to experimental errors in recoil corrections when transitioning from hydrogen to muonic hydrogen.
- Others argue that the recoil corrections are likely too small to account for the observed difference, indicating a need for further investigation.
- A participant expresses skepticism about sensationalism in reporting the findings, referencing the vacuum catastrophe as a related issue.
- There is a discussion about whether the smaller proton size implies changes in other quantities, such as proton mass, with some asserting that the charge radius is the primary concern.
- Some participants clarify that QED does not directly deal with protons, while others challenge this by stating that QED corrections are indeed relevant in Lamb shift calculations.
- The concept of size is debated, with distinctions made between geometric volume and charge radius, and the implications of these definitions on the findings.
- References to specific calculations and papers are made, highlighting the complexity of the issue and the need for further research.
Areas of Agreement / Disagreement
Participants express a range of views, with no clear consensus on the implications of the proton size discrepancy or the role of QED in the calculations. Disagreements exist regarding the interpretation of experimental data and theoretical frameworks.
Contextual Notes
Limitations in the discussion include unresolved assumptions about the nature of proton size, the dependence on definitions of size, and the complexity of the calculations involved in the Lamb shift. The discussion reflects ongoing uncertainty in the field.
Who May Find This Useful
Researchers and enthusiasts in the fields of physics, particularly those interested in quantum mechanics, particle physics, and experimental measurements of fundamental constants.
- #32
petergreat
- 266
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Forgive me for asking a naive question. Is it possible to determine the proton size using muon-proton scattering in an accelerator? Would this method be sufficiently accurate to shed light on this problem?
- #33
sanman
- 737
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Proton Smaller Than Previously Thought?
There have been a spate of articles about the size of the proton being measured as smaller than previously believed:
http://arstechnica.com/science/news/2010/07/-we-may-have-been.ars
What is the significance of this finding? What impact does it have on the broader picture?
This sounds like some basic things in physics are going to have to be revised, no matter what.
Does this affect things like nuclear cross-section values for nuclear energy applications?
There have been a spate of articles about the size of the proton being measured as smaller than previously believed:
http://arstechnica.com/science/news/2010/07/-we-may-have-been.ars
What is the significance of this finding? What impact does it have on the broader picture?
This sounds like some basic things in physics are going to have to be revised, no matter what.
Does this affect things like nuclear cross-section values for nuclear energy applications?
- #34
jtbell
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Threads merged. Sanman, check out the previous posts. I left your post intact because it has a reference to another article on the subject.
- #35
sanman
- 737
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jal said:
What about experimenting with μ+ and the anti-proton?
Shall we hope for similar results there? Or could you see a CP-violation on top of everything?
- #36
Dadface
- 2,489
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sanman said:
Interesting I think but so incredibly difficult and I would guess impossible at the present time.Just one problem that comes to mind is how are you going to get and keep a sufficient supply of anti protons or anti hydrogen?Another incredibly difficult experiment would be to test tauonic hydrogen.Experiments for the future perhaps.
- #37
Orion1
- 961
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Rydberg constant...
Was the Rydberg constant and proton radius QED equation published in the Nature article?
Does anyone disagree with this quantum mechanical definition of the Rydberg constant?
Rydberg constant:
R_\infty = \frac{m_e e^4}{8 \epsilon_0^2 h^3 c}
[/Color]
Reference:
http://en.wikipedia.org/wiki/Rydberg_constant"[/URL]
http://www.nature.com/nature/journal/v466/n7303/abs/nature09250.html"
[URL]http://books.google.com/books?id=DliKdTg8GHQC&pg=PA146"[/URL]
Nature said:
Was the Rydberg constant and proton radius QED equation published in the Nature article?
Does anyone disagree with this quantum mechanical definition of the Rydberg constant?
Rydberg constant:
R_\infty = \frac{m_e e^4}{8 \epsilon_0^2 h^3 c}
[/Color]
Reference:
http://en.wikipedia.org/wiki/Rydberg_constant"[/URL]
http://www.nature.com/nature/journal/v466/n7303/abs/nature09250.html"
[URL]http://books.google.com/books?id=DliKdTg8GHQC&pg=PA146"[/URL]
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