Lattice Quantum Chromodynamics

Date :From 2009-07-06 To 2009-07-25
Advisory committee :
Local coordinators :Ying Chen, Chuan Liu, Yu-Bing Liu, Jian-Ping Ma, Jian-Bo Zhang
International coordinators :Anthony Kennedy, Chuan Liu, Keh-Fei Liu, Jian-Ping Ma, Akira Ukawa

The last few years have seen steady and growing success of applying lattice field theory to solving problems in high energy and nuclear physics. Lattice quantum chromodynamics (LQCD) calculations with ever increasing precision have been making meaningful and, in some cases, indispensable contributions to the experimental programs.

Lattice QCD is a lattice regularized gauge theory which lends itself to Monte Carlo simulation. It is capable of calculating, from first principle, hadron masses, decay constants, elastic hadron-hadron scattering, hadron form factors, moments of parton distribution functions, weak matrix elements, topological structure of the vacuum, phase transitions at finite temperature and finite density, etc.

Hadron physics has witnessed a revival of strong interest in hadron spectroscopy in the last few years due to various new ways to probe hadron states, such as J/Ψ, D and B decays, pˉp annihilation, backward Compton scattering, reactions, and electroproduction where many glueball and exotic meson and possible pentaquark baryon candidates are discovered. Recently, progress on the broad resonance _(600), the lowest excitation in QCD, has been made in dispersion analysis of __ scattering via the Roy equation as well as lattice calculations. The existence of _(600) has important implication on the _I = 1/2 rule in K ! __ decays. From the electromagnetic and weak interference in electron scattering on nucleon, the strangeness content, such as the strangeness electromagnetic form factors can be measured experimentally. The quark and glue spin content in the nucleon has remained an unresolved topic in deep inelastic scattering. Lattice QCD is in a unique position to address these issues and progress has been made to calculate exotic hadrons and hadron structure with dynamical fermion configurations and with the inclusion of disconnected insertions and quark-antiquark annihilations. In view of the e+e? collider facility at IHEP Beijing, the glueball and exotic meson calculation should be of interest to the experimental J/Ψ decay programs at BES.

Leptonic and semi-leptonic decays of heavy-light quarkonia such as B and D mesons are the primary test grounds to study CP violation. Since the quark decays inside a hadron, both experimental and lattice calculation are needed to extract the CKM matrix. BES at BEPC has been detecting D meson decays. Lattice calculation of weak matrix element should likewise be of interest to the experimental program in IHEP as well as the high energy community in China.

Inspired by the discovery of an almost ‘perfect’ fluid in relativistic heavy ion collision experiments at Brookhaven, there are a lot of theoretical activities in high temperature QCD and finite density to understand the new phase. These include lattice QCD calculations to pin down the critical point, the dissolution of charmonium at high temperature, the study of shear viscosity to entropy ratio and the energy loss of quarks in the quark gluon plasma via gauge/gravity correspondence in the framework of ADS/CFT, the random matrix approach to the finite chemical potential, etc. In general, it remains a great challenge to map out the QCD phase diagram. The predicted color superconductor and kaon condensate phases are relevant to the core of neutron stars. Lattice QCD, on the hand, is handicapped by the severe sign problem at low temperature and high baryon numbers.

It is against the backdrop of the advances and challenges in LQCD and its present and potential relevance to experiments that we propose to hold a three-week long workshop on the topic prior to the lattice conference. The purpose of the workshop is to bring experts from the field together to discuss physics of mutual interest and for the benefit of other participants, to prepare students, postdocs and novices to the field for the lattice conference after the workshop, and, moreover, to stimulate new ideas and encourage joint projects between visitors and physicists in China.