Monday, September 19, 2016

Antimatter Responds To Gravity Like Ordinary Matter

Experimental evidence from colliders establishes that the way that antimatter responds to gravity (at least in the case of anti-electrons, called positrons) is the same as the way ordinary matter does to a precision of 0.13%.  This contradicts the hypothesis that anti-matter has an opposite gravitational charge to ordinary matter.

6 comments:

Onur said...

From the abstract:

Here we establish an indirect bound of 0.13% on the difference between the gravitational and inertial masses of the positron (antielectron) from the analysis of synchrotron losses at the Large Electron-Positron collider (LEP).

So what would be the difference between the gravitational and inertial masses of the positron if antimatter had an opposite gravitational charge to ordinary matter?

andrew said...

-200.00%.

Onur said...
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Onur said...

Thanks. Is 0.13% an expected number if antimatter responds to gravity in the same as the way ordinary matter does? Should not it be 0.00% instead?

andrew said...

The 0.13% figure is the maximum deviation consistent with the experimental margin of error. It would be equally correct to describe it as 0.00%-0.13% at a two sigma confidence interval. Given that there is inevitably statistical error and systemic error in any measurement it can't be 0.00% quoted in the way that it was. A best fit number was not quoted in the abstract and I haven't scoured the full paper enough to see if there is one, but it will definitely be closer to 0.00%.

Honestly, as the first definitive experimental measure of this quantity is sets the precision bar far higher than I would have expected. It is sufficient to rule out the anti-matter is repulsive hypothesis at the 1,538 sigma level, which is easily sufficient to constitute a discovery by particle physics standards.

Onur said...

Thanks for all the info, Andrew. That was exactly what I guessed because 0.13% is too low a figure that it is probably a statistical fluke.