In Which Nature Makes an Embarrassing Error

In the latest LHC story I just wrote about earlier, the Nature news post I linked actually has a pretty embarrassing error. This is particularly bad since Nature is one of the premier journals in most fields. For reference, you can find the ATLAS and CMS slides here.

In case they edit the text, the Nature post says that each of the photons has an energy of 750 GeV, giving a total energy of 1.5 TeV. There is one problem here that I noticed (well, if I ignore the article saying that the photons have the same mass – technically true but not really what I think the author meant to say): The photons shouldn’t both have the same energy. While the two colliding protons have approximately the same energy, the momentum transferred is high enough that the collision isn’t really proton on proton but rather parton on parton. The center of mass frame relevant to the event is not in general going to be the lab frame, so everything needs to be boosted to get to the lab frame.

This isn’t really a problem since there’s an obvious explanation: The author is talking about the center of mass frame but didn’t explicitly say so. Unfortunately, this is not true in this case. If you look at both the ATLAS and CMS slides (look for the diphoton resonance/exotics search parts), it is very clear that the center of mass energy of the two photons is 750 GeV, not 1500 GeV.