Quarkonium physics at the dawn of the LHC era.

More than a hundred experimentalists and theorists met at DESY in October to discuss the latest advances in quarkonium physics. The Quarkonium Working Group (QWG) formed in 2002 to further research in all aspects of quarkonium physics and to bridge communication between theory and experiment in the field. The group has since sponsored a series of workshops on quarkonium physics, starting at CERN in November 2002 (CERN Courier March 2003 p6 and CERN Courier September 2006 p46). The latest meeting took place at DESY, Hamburg, on 17-20 October 2007. Hot topics included recent advances in the theory of quarkonium production at the Tevatron and the B-factories; quarkonium production and in-medium behaviour in heavy-ion collisions; the new narrow-resonance states discovered by the Belle, BaBar and CLEO experiments; applications of quarkonium physics to the search for physics beyond the Standard Model; and quarkonium experiments in the LHC era. Quarkonium physics has played an important role in establishing QCD as the accepted theory of strong interactions. It has decisively contributed to the development of the quark model of hadrons and to the understanding of the properties of QCD. It also provides a unique window into the interplay between perturbative and nonperturbative QCD. Asmore » such, quarkonium physics remains at the forefront of QCD research and is an important testing ground for state-of-the-art computational tools for QCD, such as effective field theories, factorization theorems, higher-order perturbative calculations and lattice QCD. The insights gained from quarkonium studies build greater confidence in predictions for Standard Model processes and, consequently, in predictions of new physics backgrounds at the LHC. The recent discovery of remarkable new resonance states in the charmonium region of the spectrum - exciting in its own right - provides further opportunities to test the theoretical framework of quarkonium physics.« less