What an interesting but exhausting week it has been here at the Snowmass workshop in Minneapolis. I wrote last week about the opening of the workshop. In the following days, we followed what seemed to me like a pretty original schedule for a workshop. Each morning, we bifurcated (or multi-furcated, if that’s a word) into overlapping parallel sessions in which the various working groups were trying to finalize their studies. There were joint sessions between groups, in which, for instance, people studying some physics frontier were interacting with the people studying the facilities or instrumentation needed to realize the physics goals. Every afternoon we have gathered for plenary (or semi-plenary) sessions, featuring short talks on the theory and experimental work undergirding some physics topic, followed by a discussion of “tough questions” about the topic that challenged its importance in the grand scheme of things and the value of pursuing an experimental program on it. We would close each day with a panel discussion on broader policy questions, such as what is the proper balance between domestic and off-shore facilities, or how to make the case for long-term science.
It is a lot of work to put together and participate in a program like this, and overall everyone did a great job of giving well-prepared and thoughtful presentations. I should also take this opportunity to thank our hosts at the University of Minnesota for their successful management of a complicated and ever-evolving program that involved 700 physicists, most of whom registered at the last minute. (And special personal thanks to my Minneapolis in-laws, who made my visit easy!)
We’ve now gotten through the closing sessions, in which we heard summary reports from all the “frontier” working groups. I’m still digesting what everyone had to say, but here is one thing I think I know: there is general agreement that the frontiers that we are organizing our science around are not themselves science topics but approaches that can tell us about many different topics in different ways. For instance, I was quite taken with the news that cosmology can help us set bounds on the total mass of the different kinds of neutrinos; this will help us understand the neutrino spectrum with complementary information to that provided by accelerator-based neutrino experiments. Everyone is really looking to the other “frontiers” to see how we can create a program of research that can attack important physics questions in the most comprehensive possible way. And I think that a number of speakers have gone out of their way to point out that discoveries on someone else’s “frontier” may fundamentally change our understanding of the world.
(On a related note, it is also clear that we are all bothered by the tyranny of Venn diagrams. I am hoping to find time to write again about how many times a graphic of three intersecting circles appeared over the course of the week, and what amount of irony was implied each time.)
Since this the US LHC blog, I should also mention that the LHC came out well in the discussions. It is clear that there is a lot of potential for understanding and discovery at this machine, both when we increase the energy in 2015 and when we (hopefully) run in a high-luminosity mode later on in which we will attempt to increase the size of the dataset by a factor of ten. We expect to learn a tremendous amount about the newly-discovered, very strange Higgs boson, and hope to discover TeV-scale particles that make it possible for the Higgs to be what it is. From a more practical point of view, it is currently the only high-energy particle collider operating in this world, and it will stay this way for at least a decade. We must do everything we can to exploit the capabilities of this unique facility.
Where do we go from here? The results of the workshop, the handiwork of hundreds of physicists working over the course of a year, will get written up as a report that is meant to inform future deliberations. It is quite clear that we have more projects that have great physics potential, and that we really want to execute, than we have the resources to execute. In some ways, it is a good problem to have. But some hard choices will have to be made, and it won’t be long until we have convened a Particle Physics Project Prioritization Panel that will be charged with making recommendations on how we do this. I’m in no position to guess the outcome, but whatever it turns out to be, I suspect that our entire field is going to have to stand behind it and advocate it if we are to realize any, if not all, of our visions of the frontiers of particle physics.