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Register a new userStudying Two-body Nonleptonic Weak Decays of Hyperons with Topological Diagram Approach
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Many decays of light baryons consisting of light $u,d,s$ quarks have been measured, and these measurements will help us to understand the decay properties of light baryons. In this work, we study two-body nonleptonic weak decays of light baryon octet $(T_8)$ and baryon decuplet $(T_{10})$ by the topological diagram approach (TDA) under the SU(3) flavor symmetry for the first time. We find that (1) the TDA and the SU(3) irreducible representation approach (IRA) match consistently in $T_{10}to T^{()}_{8,10}P_8$ ($P_8$ is the light pseudoscalar meson octet); (2) almost all relevant not-yet-measured $mathcal{B}(T_{10}to T_8 P_8)$ may be predicted by using three experimental data of $mathcal{B}(Omega^-to Xi^0pi^-,Xi^-pi^0,Lambda^0K^-)$, and the upper limits of $mathcal{B}(T_{10}to T{}_{10}pi^-)$ may be obtained from the experimental upper limit of $mathcal{B}(Omega^-to Xi^{*0}pi^-)$ by both the TDA and the IRA together, nevertheless, all new predicted branching ratios are too small to br reached in current experiments; (3) $T_8to T_8 P_8$ decays are quite complex in terms of the TDA, and we find that W-exchange diagrams give large and even dominant contributions by using relevant experimental data and the isospin relations.
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The semileptonic decays and two-body nonleptonic decays of light baryon octet ($T_8$) and decuplet ($T_{10}$) consisting of light $u,d,s$ quarks are studied with the SU(3) flavor symmetry in this work. We obtain the amplitude relations between different decay modes by the SU(3) irreducible representation approach, and then predict relevant branching ratios by present experimental data within $1 sigma$ error. We find that the predictions for all branching ratios except $mathcal{B}(Xirightarrow Lambda^0pi)$ and $mathcal{B}(Xi^*rightarrow Xipi)$ are in good agreement with present experimental data, that implies the neglected $C_+$ terms or SU(3) breaking effects might contribute at the order of a few percent in $Xirightarrow Lambda^0pi$ and $Xi^*rightarrow Xipi$ weak decays. We predict that $mathcal{B}(Xi^{-}rightarrow Sigma^0mu^-bar{ u}_mu)=(1.13pm0.08)times10^{-6}$, $mathcal{B}(Xi^{-}rightarrowLambda^0mu^-bar{ u}_mu)=(1.58pm0.04)times10^{-4}$, $mathcal{B}(Omega^-rightarrowXi^0mu^-bar{ u}_mu)=(3.7pm1.8)times10^{-3}$, $mathcal{B}(Sigma^-rightarrow Sigma^0e^-bar{ u}_e)=(1.35pm0.28)times10^{-10}$, $mathcal{B}(Xi^-rightarrow Xi^0e^-bar{ u}_e)=(4.2pm2.4)times10^{-10}$. We also study $T_{10}to T_8 P_8$ weak, electromagnetic or strong decays. Some of these decay modes could be observed by the BESIII, LHCb and other experiments in the near future. Due to the very small life times of $Sigma^0$, $Xi^{*0,-}$, $Sigma^{*0,-}$ and $Delta^{0,-}$, the branching ratios of these baryon weak decays are only at the order of $mathcal{O}(10^{-20}-10^{-13}$), which are too small to be reached by current experiments. Furthermore, the longitudinal branching ratios of $T_{8A} to T_{8B} ell^- bar{ u}_ell~(ell=mu,e)$ decays are also given.
A previous analysis of two-body Cabibbo allowed nonleptonic decays of $D^0$ mesons and of Cabibbo allowed and first-forbidden decays of $D^+$ and $D_s^+$ has been adjourned using more recent experimental data and extended to the Cabibbo forbidden decays of $D^0$. Annihilation and W-exchange contributions as well as final state interaction effects (assumed to be dominated by nearby resonances) have been included and are in fact crucial to obtain a reasonable agreement with the experimental data, which show large flavour SU(3) violations. New fitting parameters are necessary to describe rescattering effects for Cabibbo forbidden $D^0$ decays, given the lack of experimental informations on isoscalar resonances. We keep their number to a minimum - three - using phenomenologically based considerations. We also discuss CP violating asymmetries.
We systematically study two-body nonleptonic decays of light lambda hyperon $Lambda to p pi^- (npi^0)$ with account for both short and long distance effects. The short distance effects are induced by five topologies of external and internal weak $W^pm$ exchange, while long distance effects are saturated by an inclusion of the so-called pole diagrams with an intermediate $frac12^+$ and $frac12^-$ baryon resonances. The contributions from $frac12^+$ resonances are calculated straightforwardly by account for nucleon and $Sigma$ baryons whereas the contributions from $frac12^+$ resonances are calculated by using the well-known soft-pion theorem in the current-algebra approach. It allows to express the parity-violating S-wave amplitude in terms of parity-conserving matrix elements. From our previous analysis of heavy baryons we know that short distance effects induced by internal topologies are not suppressed in comparison with external $W$-exchange diagram and must be included for description of data. Here, in the case of $Lambda$ decays we found that the contribution of external and internal $W$-exchange diagrams is sizably suppressed, e.g., by one order of magnitude in comparison with data, which are known with quite good accuracy. The major role to get consistency with experiment play pole diagrams.
We analyze $D to P V$, $D to PP$ and $D to VV$ decays within a model developed to describe the semileptonic decays $D to V l u_l$ and $Dto P l u_l$. This model combines the heavy quark effective Lagrangian and chiral perturbation theory. We determine amplitudes for decays in which the direct weak annihilation of the initial $D$ meson is absent or negligible, and in which the final state interactions are small. This analysis reduces the arbitrariness in the choice of model parameters. The calculated decay widths are in good agreement with the experimental results.
We analyze charm meson semileptonic $D to V l u_l$ and $Dto P l u_l$ and nonleptonic $D to P V$, $D to PP$ and $D to VV$ decays within a model which combines the heavy quark effective Lagrangian and chiral perturbation theory.
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