Particle physicists in the United States, aiming to organize their thinking and make it easier to explain their views to each other and to the outside world, meet every few years in workshops to consider the future of the field. (Something like this is done in a number of other scientific fields as well.) Right now, particle physics is commonly described as pursuing three general research directions:
- The Energy Frontier: Try to make new heavy particles or other high-energy phenomena using very high-energy high-collision-rate accelerators (such as the Large Hadron Collider)
- The Cosmic Frontier: Let the Universe itself, through its natural particle production mechanisms, teach us something (through properties of “dark energy” or dark matter or through cosmic rays, etc.)
- The Intensity Frontier: Search for rare new phenomena or difficult-to-produce new particles using medium-energy ultra-high-collision-rate accelerators, or some other low-energy ultra-high-rate mechanism.
With the U.S. currently out of the business of the Energy Frontier (the Tevatron having closed and there being no plans for future accelerators here) the Department of Energy has recently asked the U.S. particle physics community to hold a large workshop on the Intensity Frontier, to bring its goals into focus.
A meeting associated with this effort is going on today through Friday, in Washington D.C. About 500 scientists from different subfields of particle physics (and also some from nuclear physics) are gathered together. The difference between a “conference” and a “workshop” is that at the latter, new work is supposed to get done, both during the meeting and back home after the meeting is over. In this case, the outcome of this effort is to include a large summary document that will serve to guide scientists, the Department of Energy, the National Science Foundation and Congress as it is decided how to spend tax-payer dollars in the best interest of the U.S. and its scientific program.
For the purpose of this workshop, the Intensity Frontier has been divided into 6 subjects:
- Heavy Quarks
- Charged Leptons
- New Particles that Interact Extremely Weakly With Known Particles
- Proton Decay
- Nucleons, Nuclei and Atoms
If time permits I’ll explain later what the main concerns are for each of these subjects.
This morning I was listening to a set of very nice overview talks, one for each subject, by some of my famous colleagues: Nima Arkani-Hamed of the Institute for Advanced Study, Kaustubh Agashe of the University of Maryland, Kate Scholberg of Duke University, Neal Weiner of New York University, Bill Marciano of Brookhaven National Laboratory, and Michael Ramsey-Musolf of the University of Wisconsin. This afternoon and tomorrow, the six corresponding “working groups” are meeting separately, exchanging and discussing ideas and results. I’ll be in the working group that I called “New Particles That Interact Extremely Weakly With Known Particles.” [The official title is “Hidden Sector Photons, Axions and Weakly-Interacting Scalar Particles” but I don’t like the title because I feel it is far too limited…] On Friday the status of the working groups will be summarized, and I may be able to provide an update at that point, time permitting.