Quark masses in QCD: a progress report

Recent progress on QCD sum rule determinations of the light and heavy quark masses is reported. In the light quark sector a major breakthrough has been made recently in connection with the historical systematic uncertainties due to a lack of experimental information on the pseudoscalar resonance spectral functions. It is now possible to suppress this contribution to the 1% level by using suitable integration kernels in Finite Energy QCD sum rules. This allows to determine the up-, down-, and strange-quark masses with an unprecedented precision of some 8-10%. Further reduction of this uncertainty will be possible with improved accuracy in the strong coupling, now the main source of error. In the heavy quark sector, the availability of experimental data in the vector channel, and the use of suitable multipurpose integration kernels allows to increase the accuracy of the charm- and bottom-quarks masses to the 1% level.Comment: Invited review paper to be published in Modern Physics Letters

Introduction to QCD sum rules

A general, and very basic introduction to QCD sum rules is presented, with emphasis on recent issues to be described at length in other papers in this volume of Modern Physics Letters A. Collectively, these papers constitute the proceedings of the {\it{International Workshop on Determination of the Fundamental Parameters of QCD}}, Singapore, March 2013.Comment: Plenary talk at the International Workshop on Determination of the Fundamental Parameters of QCD. To be published in Mod. Phys. Lett.

Deconfinement and Chiral-Symmetry Restoration in Finite Temperature QCD

QCD sum rules are based on the Operator Product Expansion of current correlators, and on QCD-hadron duality. An extension of this program to finite temperature is discussed. This allows for a study of deconfinement and chiral-symmetry restoration. In addition, it is possible to relate certain hadronic matrix elements to expectation values of quark and gluon field operators by using thermal Finite Energy Sum Rules. In this way one can determine the temperature behaviour of hadron masses and couplings, as well as form factors. An attempt is made to clarify some misconceptions in the existing literature on QCD sum rules at finite temperature.Comment: Invited talk at CAM-94, Cancun, Mexico, September 1994. 21 pages and 8 figures (not included). LATEX file. UCT-TP-218/9

Electromagnetic Form Factors of Hadrons in Dual-Large NcN_c QCD

In this talk, results are presented of determinations of electromagnetic form factors of hadrons (pion, proton, and $\Delta(1236)$) in the framework of Dual-Large $N_c$ QCD (Dual-$QCD_\infty$). This framework improves considerably tree-level VMD results by incorporating an infinite number of zero-width resonances, with masses and couplings fixed by the dual-resonance (Veneziano-type) model.Comment: Invited talk at the XII Mexican Workshop on Particles & Fields, Mazatlan, November 2009. To be published in American Institute of Physics Conference Proceedings Serie

Finite energy chiral sum rules in QCD

A set of well known chiral sum rules, expected to be valid in QCD, is confronted with experimental data on the vector and axial-vector hadronic spectral functions, obtained from tau-lepton decay by the ALEPH collaboration. The Das-Mathur-Okubo sum rule, the first and second Weinberg sum rules, and the electromagnetic pion mass difference sum rule are not well saturated by the data. Instead, a modified set of sum rules having additional weight factors that vanish at the end of the integration range on the real axis, is found to be precociously saturated by the data to a remarkable extent.Comment: 6 pages, 6 figures. Invited talk at WIN99, 17th International Workshop on Weak Interactions and Neutrinos, Cape Town, South Africa, January 1999. To be published in the proceedings (World Scientific