Monday, 30 June 2008

Hidden charm in South Carolina

This last week I've been enjoying the hospitality of the University of South Carolina, where the The Eighth International Conference on Hyperons, Charm and Beauty Hadrons, a.k.a. "BEACH 2008", has just concluded. I presented an invited review of the new "hidden charm" states, focussing on results from my experiment, Belle: we have taken the lead in finding, and trying to characterise, a number of these new mesons, so called because they have both a charm quark and charm antiquark in their makeup, and thus have no charm (!) overall. Some of these particles just don't fit. Known mesons are built from a quark and an antiquark, and this structure gives rise to certain expected properties, different from those of the new states. So, we believe, these particles are put together in some other way.

The slides from my talk can be found here. The key result comes at the end: we see evidence for two more hidden-charm states that carry electric charge, something it's impossible for a conventional charm-anticharm meson (a "charmonium" state) to do. We found evidence for the first such state last year: this article from CERN Courier gives a brief description. Our paper on the latest results, which we'll submit to the Physical Review soon, can be found at arXiv:0806.4098 [hep-ex].

The early slides of my talk cover a quite different topic: charm mixing, previously mentioned on this blog. There's an historical and personal reason for this. I was supposed to present a review of mixing at the seventh BEACH meeting in Lancaster two years ago, but got very unpleasantly sick after a visit to Beijing, and ended up stuck in a hospital bed "back home" in Japan. (The glamour of international work and travel can be over-stated.) So it felt only right to include a brief update, in lieu of the review I couldn't give in '06. And it was nice to actually make it this time.