It is great to be a member of the US LHC blogging team! I have followed my friends’ posts here for a while. I hope I have something to add to the conversation, but I am confident that at least one person will read this regardless of the content because I sent the link to my Mom. (Hi, Mom!)
I’m typing on the flight back to the US from the UK after a week of meetings relating to possible future upgrades of the ATLAS detector that took place at Oxford University. I can imagine you are thinking, “Upgrades?! You people just started taking data! What are you doing already thinking about upgrades?!” I feel that way myself sometimes when numbers like 2017 and 2021 are floating around the room, particularly when I know that collisions are happening that very moment in the center of the ATLAS detector. But it is difficult to imagine a physics scenario where we would not want to see data from the LHC for a few decades. To enable this to happen people had to start thinking about upgrades well before we started taking data.
So, what is the physics landscape? Let us imagine that we find something that we think is the higgs boson. It is going to take quite a bit of data to convince ourselves that what we see is the same higgs boson that is described in our standard model of particle physics, and not some other object, like a higgs described by supersymmetry. This detective work will require high statistics, which means lots of collisions, which means lots of time with the LHC running. If we do not see anything with our first few years of running we will be able to rule out the version of the higgs boson that comes from our standard model and we will have to throw ourselves into hunting for particles and processes that are more difficult to see and, again, require more statistics. We have reasons to believe that we will see something new at the energy that the LHC was designed to deliver, but some of these scenarios will require impressive experimental gymnastics, to say nothing of (seeing a trend here?) high statistics. In order to more efficiently deliver these high statistics, the LHC has plans for upgrades of its own, and ATLAS will need to respond by making changes to the detector that allow us to cope with more extreme running conditions from the collider.
There are a few reasons running for long periods of time require upgrades to ATLAS and the other detectors, even without an upgraded LHC. For one thing, some of the electronics in our detector date back to the late 1990s and we cannot expect them all to survive well into the 2020s. There also will be pretty high flux of particles delivered to the detector over the course of data-taking, particularly to the regions close to the proton-proton interaction point, so replacement parts will be needed. Let me try an analogy: You just bought a car. It would be odd to not get regular oil changes, to keep it running well as long as is possible. And if something happens to the muffler it makes sense to replace it, even if it means spending a bit more money, in order to get the most out of the initial investment. The world has certainly invested in the LHC. (Thank you, world!) Before we go forward with specific upgrade projects we need to convince each other, our funding agencies, and the people who set the budgets of our funding agencies that the projects are justified both scientifically and financially. The peer review process rightfully keeps us on our toes.
In addition to the presentations and discussions at Oxford there were a few free moments during which we were able to explore the area. I visited the pub where J.R.R. Tolkien and C.S. Lewis used to hang out. I also visited the impressive Museum of Natural History. To top it all off, we had our workshop dinner in the Keble College dining hall, which doesn’t sound very impressive until you see the space. Harry Potter could have rounded the corner at any minute and none of us would have blinked.
Thanks for reading!