Thursday, April 02, 2009

MAMI and beyond, Day Four

Today's first talk was Fabio Ambrosino (INFN Napoli) speaking about flavour physics at the 1 GeV scale. Of course, flavour physics here does not mean charm or B-physics -- the topic was instead the accurate determination of |Vud| and |Vus| from nuclear transitions and Kaon decays. The very accurate results obtained there confirm the unitarity of the first row of the CKM matrix to great accuracy, as well as confirming universality (via a comparison of Gμ and GF).

The next talk was by Christoph Hanhart (Forschungszentrum Jülich), who spoke about QCD exotics such as hybrids, glueballs, tetraquarks and hadronic molecules. Here I learned what the physical difference between a tetraquark and a mesonic molecule (who after all both consist of two quarks and two antiquarks) is: since hadrons (as opposed to quarks) can go on-shell, the S-matrix elements for a hadronic molecule (but not a tetraquark state) would contain non-analyticities.

The remainder of the day had talks mostly about hypernuclear physics (hypernuclei are nuclei with a nucleon replaced by a strange baryon), which I feel unable to summarise (I only remember that hypernuclei are smaller and more tightly bound than normal nuclei), and accelerator physics, which I skipped in order to look after my email and a couple of papers that are in the final pre-arXiv stages of the pipeline.