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This is a potentially impactful experimental result in my niche field, the physics of relativistic laser phenomena. People have been running simulations and ima

This is a potentially impactful experimental result in my niche field, the physics of relativistic laser phenomena. People have been running simulations and imaging what RR would look like for years, and this looks like the first experimental result that shows it The money shot, fig. 9 is a bit underwhelming to me though, because it is supposed to show where the "classical model" diverges from the quantum model, and I feel queesy making a trend out of three points (one point in the blue even looks like it could touch the classical model). I'd have to read into it more (will do, just not tonight). This is, however, an extremely difficult experiment to perform, hence why they only have four data points. They definitely have demonstrated that RR does occur (no duh, which is more of why it's a good paper) but I'd hold off on the claim they've really distinguished the two. Cheers to ICL on this first.

im3w1l 9y ago
The article is a little hard to understand. First I thought the electrons were in frontal collisions with light and was like "duh of course it slows down". But then they talked about the electrons hit a "sheet" of light. So is the correct interpretation that the light and electons hit at perpendicular angles (in the lab reference frame)?
sofasurfer 9y ago
I’d say that the main conclusion is the observation of a statistically significant (> 3 sigma) radiation reaction effect which is pretty consistent with both the classical model and the quantum model. The data “hints” that the quantum one fits the data better, but not at a very significant level (1 sigma). Moving to higher electron energies and/or laser intensities will help make that difference clearer. The paper is not called “first observation of quantum radiation reaction” for a reason.
- noobermin 9y ago
  Exactly. 10^21 W/cm^2 is actually a little below the threshold of where we expected RR (which is what the second Gemini beam shot at), and hitting 0.5 GeV electrons head-on helped alleviate that restriction. With a host of planned laser systems exceeding 10^22 W/cm^2, we can imagine more statistically significant divergences between QRR and Landau-Lifshitz (the "classical" RR model).

im3w1l 9y ago

The article is a little hard to understand. First I thought the electrons were in frontal collisions with light and was like "duh of course it slows down". But then they talked about the electrons hit a "sheet" of light. So is the correct interpretation that the light and electons hit at perpendicular angles (in the lab reference frame)?

sofasurfer 9y ago

I’d say that the main conclusion is the observation of a statistically significant (> 3 sigma) radiation reaction effect which is pretty consistent with both the classical model and the quantum model. The data “hints” that the quantum one fits the data better, but not at a very significant level (1 sigma). Moving to higher electron energies and/or laser intensities will help make that difference clearer. The paper is not called “first observation of quantum radiation reaction” for a reason.

noobermin 9y ago
Exactly. 10^21 W/cm^2 is actually a little below the threshold of where we expected RR (which is what the second Gemini beam shot at), and hitting 0.5 GeV electrons head-on helped alleviate that restriction. With a host of planned laser systems exceeding 10^22 W/cm^2, we can imagine more statistically significant divergences between QRR and Landau-Lifshitz (the "classical" RR model).