Project X workshop November 19, 2007Posted by apetrov in Particle Physics, Physics, Science.
I got back from Fermilab, where I stayed for a day of a Project X workshop. This workshop is the second in a series of trying to chart the intermediate future of Fermilab — in other words, in between 2009 when we loose Tevatron until 202X when the International Linear Collider (ILC) will be operational at FNAL (ok, I’m an optimist here). The first workshop was about accelerator issues, i.e. technical aspects of high intensity source at FNAL. So this one was regarding building the “physics case”, i.e. what physics one can do at the “intensity frontier” with that machine. I was curious what would be the outcome of that workshop – you see, there originally was an “intermediate project” – it was called BTeV and it was supposed to study flavor physics. So to make the long story short, I actually was in “physical” attendance for the first day of the conference and was asked to connect “virtually” for the second day (I participated in the “antiprotons” working group).
Instead of reporting about the workshop (you can actually look at the transparences of the talks here), I want to convey the atmosphere of what was happening there, in particular concentrating on the talk by Jon Bagger (which had the gist of what other theorists, Joe Lykken and Hitoshi Murayama also said). It was a bit surprizing to me to see Jon give a Project-X talk, since, as far as I know, he was the one of the biggest proponents to streamline the the high energy physics program by consolidating the efforts of most of the US physicists around ILC (which practically resulted in the cancelation of BTeV and a number of other flavor physics experiments with great physics programs such as RSVP or CKM). He concentrated on three physics topics that one can do with this device: quark flavor physics (kaon rare decays), charged lepton flavor physics (muon transitions via flavor-changing neutral currents (FCNC)) and neutrino physics. Indeed those are the things one can do with 8 GeV super-intense proton beams.
The point is that LHC might not be sensitive to flavor physics of the first two generations, i.e. how new physics at the TeV-scale couples to them. That used to be the reason to do flavor experiments — and continues to be in Japan and at CERN. The only thing that we know now that we didn’t know when the plug was pulled on experimental flavor physics effort in the US is that the Nature happened to be following the concept of “Minimal Flavor Violation” (or MFV) – or very close to it. Which means that whatever new physics awaits us at a TeV-scale, for some reason it chose to communicate itself to low energy scales by the Standard Model-like operators. We were hoping for spectacular results in B (or charm) physics, but it didn’t happen… and we don’t know why.
What was interesting in his talk are the messages that he decided to draw — and which gave him a very hostile reception. First, he asked if “some experiments could be done cheaper elsewhere” (yes, indeed – as someone in the audience noted, the US can simply NOT do any HEP experiments and wait for the Europeans/Chineese/Japaneese physicists to do them — but is this a good approach?). Second, Jon said that “detailed calculations needed to convince everybody of the importance of Project X in the world flavor program” (that drew lots of emotions from people who were on the cancelled Fermilab kaon experiments, which passed the physics studies with flying colors). I actually think that one does need to go back to the drawing board here. First of all, feasibility of new kaon experiments was not demonstrated for the high-intensity setup project X is going to be. Second, one needs to see if the expected results will improve on the approved CERN and KEK experiments. Of course, having an estimated statistics of 800-1000 events for a kaon experiment in Project-X in the FCNC channel K+ -> pi+ nu nu-bar is great! Finally, Jon said the following: “If Project-X positions Fermilab as a credible host [for ILC], it might be well worth the effort. If not — it will be a mistake”… It’s an interesting statement that reflects the ILC-centric views of many in US high energy physics (BTW, the preceeding talk by David McGinnis actually stated that accelerator issues in Project X are very much alligned to what one expects to have at the ILC). But, as many people later complained in private conversations, it significantly narrows the scope of US particle physics program. In particular, it implies that studying QCD is not worth the effort. So here is the gist of it — we report, you decide :-).
One of the impressions that I got at this conference is that how difficult it would be so see if Project X has an easy place to be in the world-wide flavor-physics effort. Many similar studies of kaon decays are done at CERN and KEK; experiments with charged leptons are being performed at PSI in Switzerland, neutrinos are being studied at CERN and KEK, and antiproton experiments will be done at GSI in Germany (PANDA) – their FAIR facility just got government approval. Of course, independent checks of the results are needed… at any rate, it’s the huge intensity of the proposed proton source that can give us an edge…
P.S. For a general discussion of the Project-X workshop (including Gene Golowich’s quote from the CHARM-2007 conference — which really has nothing to do with that particular Project-X workshop, but tells you something about the status of flavor physics in the US) see here.