arXiv subjects
Publications and source records attributed to Dongsheng Liu.
We demonstrate that a $u-d$ mass difference (which we estimate to be about 4 MeV) within quantum loops, can reproduce the effects of the Coleman-Glashow electromagnetic tadpole operator.
We prove that recent data demonstrates unequivocally that the scalar meson $f_0$(980) is mostly composed of $s\bar{s}$ quarks and that the coupling of $f_0$ to photons and mesons is in agreement with the linear sigma model.
We give best covariant amplitude decompositions for two-body decay processes involving ground state hadrons ($0^-, 1^-, {1/2}^+, {3/2}^+$) and show how these are simply related to helicity amplitudes. After discussing how electromagnetic interactions are incorporated via meson dominance in a relativistic supermultiplet scheme, we extend the analysis to weak flavour changing nonleptonic processes. Such weak interactions are described by three generic amplitudes, which we estimate according to the rules of calculation within covariant SU(2N$_f$).
We provide succinct covariant amplitude decompositions of 2-body weak hadronic decays, with which to compare data, including exclusive rates, helicity amplitudes and polarizations. For weak decays, the systematic dependence of these amplitudes on masses and quantum numbers of participating particles are determined within a factor of about two by the CKM angles and the Fermi constant so theoretical models need to be much more accurate if they are to be convincing.
The radiative meson decays $V\to Pγ$ and $P\to γγ$ are analyzed using the quark triangle diagram. Experimental data yield well determined estimates of the universal quark-antiquark-meson couplings $g_{Vq\bar{q}'}$ and $g_{Pq\bar{q}'}$ for the light meson sector. Also predictions for the ratios of neutral to charged heavy meson decay coupling constants are given and await experimental confirmation.
It is possible to express all the strong and electromagnetic interactions of ground state hadrons in terms of a single coupling constant and the constituent quark masses, using spin-flavour relativistic supermultiplet theory. Results are generally accurate to within 10%.
We analyze forward-backward charge asymmetry of the lepton production in rare decays $B\rightarrow X_s l^+l^-$ and $B\rightarrow K^* l^+l^-$, including vector-resonance effects. Certain regions of phase space, in which the asymmetry is sensitive to individual short-distance coefficients, are pointed out. In particular, we suggest a method to test the coupling of the leptonic axial vector current to the left-handed quark current experimentally.
Forward-backward charge asymmetry in rare dilepton $B$-decays is formulated with the assumption of an on-shell b-quark. We find the asymmetry is expressed in terms of two spatially transverse helicity amplitudes, which are determined by combining the data of $D\rightarrow K^*(892)\; l^+ ν$ with heavy flavour symmetry. We estimate the charge asymmetry of $B\rightarrow K^*(892)\; l^+ l^-$ for large energy leptons against various top masses in the standard model.
We analyse the Lorentz structures of weak decay matrix elements bewteen meson states of arbitrary spin. Simplifications arise in the transition amplitudes for a heavy meson decaying into a light one via a Bethe-Salpeter approach which incorporates heavy quark symmetry. Phenomenological consequences on several semileptonic, nonleptonic and FCNC induced decays of heavy flavoured mesons are derived and discussed.
Lorentz covariant wave functions for meson and baryon supermultiplets are simply derived by boosting $SU(2)_J$ representations corresponding to multiquark systems at rest.
We estimate the non-leptonic B decays $B \rightarrow (ψ,ψ^\prime , χ_{1c})+K^i$, where $K^i$ are various K-meson resonances. We use the model of Isgur, Wise, Scora and Grinstein in the context of heavy quark effective theory, to calculate the hadronic matrix elements. Our estimates show that a substantial fraction of $B \rightarrow X_s ψ$ results in higher resonances of K-meson and besides $B \rightarrow K(K^*) ψ$, a considerable fraction of $B \rightarrow X_s (c\bar c)$ goes to $B \rightarrow (K,K^*)+( ψ^{\prime},χ_{1c})$.
The renormalization effects from the b-quark scale down to the non-perturbative QCD regime are studied for rare $B$-decays at the heavy b-quark limit. Phenomenological consequences of these effects are investigated. We find that the anomalous scaling behavior plays a positive role in making non-perturbative model calculations consistent with recent CLEO measurements of $B\rightarrow K^* γ.$
We use the new symmetries in the heavy quark limit to calculate the exclusive B-decays $B \rightarrow K^i ψ$ where $K^i$ are higher resonances of K-meson. We then estimate the long distance contributions to $B \rightarrow K^i γ$ decays via $ψ- γ$ conversion. The results point to around $30 \%$ uncertainty in the top quark mass determined by measurements of rare B-decays $B \rightarrow K^i γ$.
We use the new symmetries in the heavy quark limit to calculate the exclusive B-decays $B \rightarrow K ψ(ψ^{\prime})$ and $B \rightarrow K^* ψ(ψ^{\prime})$. The estimated decay rates are compared with experimental values. We also estimate rare $B \rightarrow K^* γ$ decay rate, based on these experimental data and heavy quark symmetry.