Research interests

My research efforts focus mainly on low energy QCD and hypernuclear physics. I am extensively involved in the investigations of a number of fundamental issues such as anomalies in QCD, SU(3) symmetry breaking, the substructure of pseudoscalar mesons p⁰, h and h^/ in terms of quark and gluon degrees of freedom, by studying the mesons’ coupling to photons via the Primakoff mechanism. I also worked on various hypernuclear physics projects at BNL and TJNAF. The hypernuclei with one or two nucleons replaced by hyperons provide a rich laboratory to study the structure of nuclei, the YN and YY interaction, and test the limit of our conventional nuclear models in solving the many body systems with additional strangeness degree of freedom.

Although we firmly believe that QCD is the ultimate theory explaining all strong interaction effects from the first principles, little progress has been made in this direction. As the traditional perturbation theory breaks down due to the quark confinement, low energy QCD remains a challenging scientific field representing one of the frontiers in contemporary physics. The three neutral pseudoscalar mesons p⁰, h and h^/, with the first two being Goldstone bosons caused by the spontaneously breaking of the chiral symmetry, while the h^/ is not due to the chiral anomaly, represent one of the most interesting system in low energy QCD.  This system contains fundamental information about the effects of SU(3) and isospin breaking by the u, d and s quark masses, leading to important mixing effects among the mesons. There is a second type of anomaly that involves the coupling of the quarks to the photon field, being directly responsible for the decays of these three mesons into photon pairs. A study of p⁰, h and h^/ system provides a powerful tool to understand QCD at the confinement scale.

Currently I am an active member of PrimEx collaboration at TJNAF, working on an approved experiment (E99-014) with A^- rating to measure the decay width G(p⁰®gg) with high precision (1.4%). The amplitude of this decay is one of the very few predictions of QCD that is relatively unambiguous, at least in the chiral symmetry limit of massless pions. The precision measurement of the p⁰  radiative decay width is widely recognized as a key experiment that bridges chiral symmetry breaking and our understanding of QCD. We are working on the development and construction of the experimental setup, including a pair spectrometer for photon flux control and a state-of-the art, high-resolution hybrid calorimeter to measure photons from p⁰ decays at small forward angles. The National Science Foundation funded this project for a $1,000,000 Major Research Instrumentation Grant in 2000 (NSF, MRI PHY-0079840). This project is a leading physics in one of the four physics frontier centers in America, which were approved by NSF in 2001.

I played a leading role in the development of the proposal, Precision Measurements of Electromagnetic Properties of Pseudoscalar Mesons at 12 GeV via the Primakoff Effect. I presented this proposal at TJNAF PAC18 special review in July 2000. It received a high recommendation from the PAC to be addressed in the executive summary of CEBAF 12 GeV upgrade white paper. In the proposal, we suggested a program to measure the radiative decay widths G(P®gg) and the transition form factors F_gg*P, where P represents h and h^/.  The decay widths of h(h^/)®gg, which proceed primarily via the chiral anomaly, lead to a direct determination of the h-h^/ mixing angle and the h^/ decay constant. The transition form factors of these mesons at small Q²(~0.001-0.5 GeV²) will provide model independent extractions of the size of the electromagnetic interaction radii of mesons, and a low energy constant in the chiral Lagrangian

           I also worked on various projects of L non-mesonic decay, H dibaryon and double L hypernuclei, and L hypernuclear spectroscopy experiments at BNL and TJNAF.  My Ph.D. thesis project was H particle search experiment (E813) at BNL. I undertook substantial responsibility for HNSS experiment (E89-009) just completed in early 2000 at TJNAF. This was the first electroproduction experiment focusing on L hypernuclear spectroscopy in the p shell with high resolution at the level of 600 KeV (FWHM). The Japanese group in our collaboration received a $3,000,000 grant in 2000 to build a new spectrometer for the future hypernuclear experiments at TJNAF.