Hoi-Lai Yu

Bio: Hoi-Lai Yu is an academic researcher from Academia Sinica. The author has contributed to research in topics: General relativity & Hamiltonian constraint. The author has an hindex of 15, co-authored 47 publications receiving 1306 citations.

Heavy-quark symmetry and chiral dynamics.

Abstract: The flavor and spin symmetry of the heavy quarks and the spontaneously broken approximate ${\mathrm{SU}(3)}_{L}\ifmmode\times\else\texttimes\fi{}{\mathrm{SU}(3)}_{R}$ chiral symmetry of the light quarks are exploited to formulate a theory describing the low-energy interactions of the heavy mesons ($Q\overline{q}$ bound states) and heavy baryons (${\mathrm{Qq}}_{1}{q}_{2}$ bound states) with the Goldstone bosons $\ensuremath{\pi}$, $K$, and $\ensuremath{\eta}$. The theory contains only three parameters independent of the number of heavy-quark species involved. They can be determined by the decays ${D}^{*}\ensuremath{\rightarrow}D+\ensuremath{\pi}$, ${\ensuremath{\Sigma}}_{c}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}+\ensuremath{\pi}$, and ${\ensuremath{\Sigma}}_{c}^{*}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}_{c}+\ensuremath{\pi}$. Theoretically, these coupling constants are related, through partial conservation of axial-vector current, to the axial charges of the heavy mesons and the heavy baryons. They are all calculable in the nonrelativistic quark model by using the spin wave functions of these particles alone. The theory is applied to strong decays and semileptonic weak decays of the heavy mesons and baryons. The implications are also discussed.

Perturbative QCD analysis of B meson decays.

Abstract: The resummation of large QCD radiative corrections, including leading and next-to-leading logarithms, in the pion electromagnetic form factor is reviewed. A similar formalism is applied to exclusive processes involving heavy mesons, and leads to Sudakov suppression for the semileptonic decay {ital B}{r_arrow}{pi}{ital l}{nu}. It is found that, with the inclusion of Sudakov effects, a perturbative QCD analysis of this decay is reliable for the energy fraction of the pion above 0.4. Combining predictions from soft pion theorems we estimate that the upper limit of the matrix element {parallel}{ital V}{sub {ital ub}}{parallel} is 2.8{endash}4.8{times}10{sup {minus}3} from different models of the {ital B} meson wave function. {copyright} {ital 1996 The American Physical Society.}

Chiral Lagrangians for radiative decays of heavy hadrons.

Abstract: The radiative decays of heavy mesons and heavy baryons are studied in a formalism which incorporates both heavy-quark symmetry and chiral symmetry. The chiral Lagrangians for the electromagnetic interactions of heavy hadrons consist of two pieces: one from gauging electromagnetically the strong-interaction chiral Lagrangian, and the other from the anomalous magnetic moment interactions of the heavy baryons and mesons. Because of the heavy-quark spin symmetry, the latter contains only one independent coupling constant in the meson sector and two in the baryon sector. These coupling constants only depend on the light quarks and can be calculated in the nonrelativistic quark model. However, the charmed quark is not heavy enough and the contribution from its magnetic moment must be included. Applications to the radiative decays ${D}^{*}\ensuremath{\rightarrow}D\ensuremath{\gamma}$, ${B}^{*}\ensuremath{\rightarrow}B\ensuremath{\gamma}$, ${\ensuremath{\Xi}}_{c}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\Xi}}_{c}\ensuremath{\gamma}$, ${\ensuremath{\Sigma}}_{c}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\gamma}$, and ${\ensuremath{\Sigma}}_{c}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\pi}\ensuremath{\gamma}$ are given. Together with our previous results on the strong decay rates of ${D}^{*}\ensuremath{\rightarrow}D\ensuremath{\pi}$ and ${\ensuremath{\Sigma}}_{c}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\pi}$, predictions are obtained for the total widths and branching ratios of ${D}^{*}$ and ${\ensuremath{\Sigma}}_{c}$. The decays ${\ensuremath{\Sigma}}_{c}^{+}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ and ${\ensuremath{\Sigma}}_{c}^{0}\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$ are discussed to illustrate the important roles played by both heavy-quark symmetry and chiral symmetry.

Hadronic molecules

Abstract: A large number of experimental discoveries especially in the heavy quarkonium sector that did not at all fit to the expectations of the until then very successful quark model led to a renaissance of hadron spectroscopy Among various explanations of the internal structure of these excitations, hadronic molecules, being analogues of light nuclei, play a unique role since for those predictions can be made with controlled uncertainty We review experimental evidences of various candidates of hadronic molecules, and methods of identifying such structures Nonrelativistic effective field theories are the suitable framework for studying hadronic molecules, and are discussed in both the continuum and finite volumes Also pertinent lattice QCD results are presented Further, we discuss the production mechanisms and decays of hadronic molecules, and comment on the reliability of certain assertions often made in the literature