The Bad Astronomy blog is publicizing a chance to choose what the Hubble Space Telescope looks at. The basic idea is that there’s going to be an internet vote between six objects that Hubble has never looked at, and Hubble will be pointed at the winner and send out pictures of it by April. It seems like a fun way to get the public to learn more about, and feel more involved in, the Hubble project.
I’ll let you read more details at one of the links above, but I have another question to consider: can we do something similar with the LHC? That is, could we put up some kind of page where people could vote on what kind of physics we would study over the course of some particular week? Maybe a choice between searching for Supersymmetry, or a high-mass Higgs boson, or a low-mass Higgs boson? At first glance, the answer would seem to be “no.” We obviously have no control over what kind of physics happens when the protons of the LHC collide — we just look at what comes out. And it seems unlikely that any physicist would volunteer to put their work hours into a particular analysis because of a public vote, and anyway we’ll have people working on all the high-profile analyses and many low-profile ones besides.
But there actually is a sense in which ATLAS or CMS could to something similar. Remember that our detectors can only record a few hundred events every second, out of the almost forty million times the beams cross during that second. There are lots of collisions we have to throw out because we can’t store enough data, and it’s the trigger system that decides which few we keep. In practice, there are a number of different signals that we program the trigger system to be interested in: we take a certain number of random low-energy events to help us calibrate what we see in our other events, and we have separate “trigger paths” for hadronic jets, for muons, for electrons, and so on. We try to record all the events that might represent interesting new physics, but as the collision rate at the LHC increases, we’ll have to throw away even some of those. When the committee meets to decide how to balance the different possible triggers, what is at issue is precisely which kinds of events the detector will “point at,” i.e. recognize as important and save. People with different interests in terms of physics might make different choices about how to achieve that balance, and every study would always love more trigger bandwidth if it were available, and that’s why we have committees to argue about it in the first place.
So why not reserve 5% of the ATLAS or CMS trigger bandwidth for a public vote on what physics to look for, to give a little extra oomph to one study or another? Actually, I can think of several good and practical reasons why not — but it’s fun to think about!