Y. C. Lin

Bio: Y. C. Lin is an academic researcher from National Central University. The author has contributed to research in topics: Chiral perturbation theory & Chiral anomaly. The author has an hindex of 10, co-authored 10 publications receiving 790 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.

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.

Corrections to chiral dynamics of heavy hadrons: SU(3) symmetry breaking.

Abstract: In previous publications we have analyzed the strong and electromagnetic decays of heavy mesons and heavy baryons in a formalism which incorporates heavy-quark and chiral symmetries. There are two possible symmetry-breaking effects on the chiral dynamics of heavy hadrons: the finite-mass effects from light quarks and the $\frac{1}{{m}_{Q}}$ corrections from heavy quarks. In the present paper, chiral-symmetry-breaking effects are studied and applications to various strong and radiative decays of heavy hadrons are illustrated. SU(3) violations induced by chiral loops in the radiative decays of charmed mesons and charmed baryons are compared with those predicted by the constituent quark model. In particular, available data for ${D}^{*}$ decays favor values of the parameters in chiral perturbation theory which give predictions for ${D}^{*}$ decays close to the quark model results except for the ${D}_{s}^{*+}$. Implications are discussed.

Heavy-flavor-conserving nonleptonic weak decays of heavy baryons.

Abstract: The heavy-flavor-conserving nonleptonic weak decays of heavy baryons are studied in a formalism that incorporates both heavy-quark symmetry and chiral symmetry. The phenomenological {Delta}{ital S}=1 nonleptonic weak chiral Lagrangian for these transitions contains two independent coupling constants that describe the transitions between two flavor-SU(3) antitriplet heavy baryons, and the transitions between two flavor-SU(3) sextet heavy baryons. In the MIT bag model and the diquark model, only transitions between antitriplets are allowed. The coupling constants for these transitions are calculated in both models. The result is applied to specific nonleptonic decays such as {Xi}{sub {ital c}}{r arrow}{Lambda}{sub {ital c}}{pi}, and the branching ratios are found to be of the order of 10{sup {minus}4}. An example of a nonleptonic decay due to symmetry breaking is provided by {Omega}{sub {ital c}}{r arrow}{Xi}{sub {ital c}}{sup {prime}}{pi}, which is estimated to have a smaller branching ratio, of the order of 10{sup {minus}5}.

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

Charm quark contribution to K+ ---> pi+ nu anti-nu at next-to-next-to-leading order

Abstract: We calculate the complete next-to-next-to-leading (NNLO) order QCD corrections to the charm contribution of the rare decay K+??+?. We present the results for the two-loop matching conditions of the Wilson coefficients, the three-loop anomalous dimensions, and the two-loop matrix elements of the relevant operators entering the NNLO renormalization group analysis of the Z-penguin and the electroweak box contribution. The NNLO QCD corrections reduce the theoretical uncertainty from ?9.8% at NLO to ?2.4% in the relevant parameter Pc(X), implying the leftover scale uncertainties in (K+??+?) and in the determination of |Vtd|, sin 2?, and ? from the K??? system to be ?1.3%, ?1.0%, ?0.006, and ?1.2?, respectively. For the charm quark mass mc(mc) = (1.30?0.05)GeV and |Vus| = 0.2248 the NLO value Pc(X) = 0.37?0.06 is modified to Pc(X) = 0.38?0.04 at NNLO and the error is fully dominated by the uncertainty in mc(mc). We tabulate Pc(X) in terms of mc(mc) and ?s(MZ) and express the dependences of Pc(X) on these and other parameters by an accurate approximate analytic formula. We find (K+??+?) = (8.0?1.1) ? 10?11 and the quoted uncertainty mainly stems from mc(mc) and the Cabibbo-Kobayashi-Maskawa elements. We also emphasize that improved calculations of the long-distance contributions to K+??+? and of the isospin breaking in the weak current matrix element will further sharpen the sensitivity of the two golden K??? decays to new physics.

The Physics of the B Factories

Abstract: This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C.