The next particle collider to be built, not counting the planned upgrade of the Large Hadron Collider at CERN, seems likely to be the “Electron-Ion Collider” (EIC) at Brookhaven National Laboratory on Long Island in the US. This will not be a machine probing the frontiers of high energy, but it will bring some exciting new capabilities, and it will indirectly help us understand the energy frontier.

The EIC will be a “QCD machine”, meaning it will provide a lot of new information about Quantum Chromodynamics, the strong force which binds quarks inside hadrons and holds protons and neutrons together inside atomic nuclei. In both the US and Europe, the EIC comes under nuclear physics rather than particle physics, because most of the ions it will collide will be bigger than the hydrogen ions (protons) that usually collide at CERN. But the exact boundary between particle and nuclear physics is pretty arbitrary, and the science of the EIC straddles it. QCD is a rich theory, with much left to be understood.

One thing the EIC has already done is to help inspire a paper submitted to the arXiv last week by some colleagues and me. The electron beam at the EIC will bring with it a beam of photons, and this paper is about modelling their interactions, using Monte Carlo simulations and data from current and previous colliders at CERN, at DESY in Hamburg, and at Fermilab near Chicago. The data are all made available at the HEPData repository and the code used to analyse them is in the Rivet library. We use all this to make some recommendations about how best to model future photon-ion collisions at EIC, as well as photon-proton and photon-photon collisions at the LHC and other possible future colliders.

This was a bit of a retread for me, since the HERA collider at DESY was where I did my early career research, and in the 1990s and 2000s I was involved in recording and analysing some of the data we used in this new paper. It is very satisfying that those measurements and analyses are still available, reprodicible and useful.

It was also pretty satisfying that three of the authors (Shazhad, Juanjo and Bradley) were undergraduate and masters students supervised by me and Matthew Wing at UCL, and that Ilkka is a colleague from Jyväskylä in Finland, an institute probably best known for its nuclear physics facilities.

Despite this excursion, I’m planning to work on the Large Hadron Collider rather than EIC for the foreseeable future, and I’m excited by its imminent upgrades. (The image on this post is from the excellent ATLAS Standard Model meeting we had last week in Ljubljana). But I think it’s great that the EIC will be starting up. As well as the knock-on benefits for the LHC from a better understanding of QCD and the structure of the proton, a new collider always seems to bring serendipitous benefits, as well as moving technology forward, both hardware and software.

I look forward to seeing what this one brings.